A man has died after being hit by a Tube train as he tried to save his brother, who had fallen on to the tracks.
Nick Mann, 35, from London, was trying to pull his 32-year-old brother, Robert, to safety at London Underground's Old Street station when they were both struck.
British Transport Police (BTP) said they are not treating the incident as suspicious, adding that it appeared to be a "tragic accident".
Nick Mann, 35, died in hospital on Sunday
The London man was taken to the Royal London Hospital, where he later died.
Police officers are appealing for witnesses to the Northern Line incident, which happened at 12.20am on Sunday.
It is thought Robert Mann may have been trying to recover an item such as a mobile phone or wallet which had fallen onto the track, the Evening Standard reports.
Robert Mann, 32, was on the tracks at Old Street
BTP said officers discovered the two men with serious injuries after being called to the station, adding: "The men, one aged 32 from Manchester and the other aged 35 from London, were treated at the scene by colleagues from the London Ambulance Service and then taken to Royal London Hospital in a critical condition.
"The 35-year-old man from London died in hospital later that day. The 32-year-old man from Manchester remains in a stable but critical condition.
Emergency crews at the scene in the early hours of Sunday
"Officers are not currently treating the incident as suspicious and are now working to put together a fuller picture of what happened."
Investigating officer Detective Sergeant Adrian Naylor said: "I am keen to speak to anyone who was at the station or on the platform when the incident happened to help us understand how the two men came to be struck by a train."
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London Underground
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The first ever London Underground journey. The station pictured is Edgware road. William Gladstone, who would become prime minister, his wife, and the engineer John Fowler were aboard 24 May 1862 (credit:Getty)
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The construction of the Metropolitan Underground Railway - work in progress at Kings Cross 05/05/1861 (credit:PA)
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The original Bank, City and South London underground station near Mansion House 01/08/1901 (credit:PA)
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Women at work in Ealing Common, upholstering railway carriages for the London Underground 01/01/1916 (credit:PA)
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An interior view of one of the carriages of the new Electric Train for the Metropolitan Railway 18/12/1919 (credit:PA)
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Lord Ashfield hands over the silver key to Col. Moore Brabazon during the opening of the new underground railway with the world's longest tunnel which ran from East Finchley to Morden on the Northern line, London. 13/09/1926
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Escalators being built at Piccadilly Circus Underground Railway Station 01/09/1928 (credit:PA)
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Unrecognised by passers-by, Britain's Princess Elizabeth, left, and her sister Princess Margaret, are taken for a walk through busy London streets on May 15, 1939, after their first ride on a London Underground train. They were accompanied by their governess and a lady-in-waiting. (credit:AP)
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Londoners sleep on stopped escalators of a tube station for safety and shelter during heavy bombing by the Germans in London, England during the blitz 01/01/1940 (credit:PA)
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Women knit and talk as they seek shelter in the tube station during heavy bombing by the Germans in London, during the blitz in World War II 01/01/1940 (credit:PA)
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People sleep in Piccadilly Underground station, London, during Nazi bombing raids. 27/09/1940 (credit:PA)
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Londoners sleep on the platform and on the train tracks at Aldwych Underground station,London, during heavy all night Nazi bombing raids 8/10/1940 (credit:AP)
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An air raid warden brings a drink of water for a young girl who has awakened during the night in an air raid shelter at the Aldwych tube station in London, during the blitz in World War II. Hammocks are slung across the train tracks for sleeping. 21/10/1940 (credit:PA)
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British comedian and actor George Formby, centre playing his ukulele, entertains people sheltering from the Nazi bombing raids, in the deep underground station at Aldwych, London 27/11/1940 (credit:AP)
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A bomb which fell during the London Blitz in January 1941 narrowly missed the Bank of England. It crashed through the roadway between the bank, Mansion House and Royal Exchange, shattering the underground subway causing many casualties. 21/01/1941 (credit:AP)
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Secret and concealed war defenses in England dotted the country. Now it safely can be told that an information booth in Trafalgar Square and a greengrocery in Kingston-on-Thames were disguised pillboxes; that an Ilford subway station was an underground munitions plant, and that the Admiralty buildingÂ’s adjunct was a invasion. In this picture, the innocent-looking fruit and greengrocery store in Kingston-on-Thames is really a cleverly camouflaged pillbox in London, England, 11/07/1945 (credit:AP)
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An underground tube train pulls into Cockfosters Station, the end station on the northbound Piccadilly Line 25 Feb 1950 (credit:PA)
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A fire engine attends an underground cables fire in Queen Victoria Street 17 Aug 1950 (credit:PA)
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Locomotive No.23, a Metropolitan 'A' Class engine, built at Manchester in 1866, heads a centenary special at Neasden as part of a grand parade of past and present rolling stock to commemorate the 100th anniversary of London's Underground 23 May 1963 (credit:PA)
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Amar Singh, the Sikh train guard who has now been given permission to wear his turban while on duty on London's Underground, with his wife, Amrid, and their 13-day-old daughter, whom they call Jaki, at their Southall, Middlesex 02 Sep 1964 (credit:PA)
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London transport underground train driver Mr. Earnest Coulson, 60, who has 41 years of service with London transport, takes his hands from the controls of the tube train as it was guided by electronic impulses on the shuttle section of the Woodford-Hainualt line in London, United Kingdom, on Feb. 19, 1968. The train picks up coded impulses from the main track which causes the train to accelerate, coast and brake to a halt at the next station, obeying all instructions given on the way, and slowing down or stopping or restarting as required if there is another train or a speed restriction on part of the route. The train operator, stationed in the front cab, closes the doors and presses the twin “start” buttons at the beginning of the run. He can also take over the in the event of failure of the automatic equipment (credit:AP Photo/Victor Boyton)
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The Queen arriving at Heathrow Central station in London in the driver's cab of a Tube Train, when she officially opened the £30 million Piccadilly Line extension linking Heathrow Airport with London's underground railway system. Pictured with her is Graeme Bruce, London Transport's Chief Operating Manager 16 Dec 1977 (credit:PA)
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Kingsway in London, England in 1971 with the large sign marking the entrance to the Chancery Lane Underground subway station 01 Jan 1971 (credit:AP)
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Forty-three people were killed after a tube train crashed through buffers and into an end wall. The photograph shows fireman at work in one of the coaches of the six-carriage London Underground train which overran the platform and entered a blind tunnel at Moorgate Station in London 28 Feb 1975 (credit:PA)
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The Queen this morning opened the new Victoria Line. It will be the first time a reigning monarch has ridden on the underground 07 Mar 1969 (credit:PA)
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A London Transport official shows the Prince of Wales the controls in the driver's car of a Jubilee Line train when the Prince took a ride from Green Park to Charing Cross on the new £87 million underground line, which runs from Stanmore to Charing Cross 30 Apr 1979 (credit:PA)
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In 1985, smoking was banned in all stations below ground.It had already been banned on trains the previous year following a fire at Goodge Street station.This however, was not enough to stop people lighting up on the escalators on their way out of atations, a situation which led to the blaze in Kings Cross which killed 31 people. (credit:Flickr/ell brown)
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The top of the fire-damaged escalators at King's Cross underground station in London. The fire, which killed 31 people, is believed to have been started on the main escalator up from the platforms when a lit match was dropped by a passenger 19 Nov 1987 (credit:PA)
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At least 31 people died and scores were injured in a major fire at London's busiest underground station at Kings Cross. Fireman are seen here in the smouldering remains of the main ticket hall in the station. 19 Nov 1987 (credit:PA)
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Transport Secretary Sir George Young standing outside St James Park tube Station in London today. Mr Young confirmed that the Government wants to privatise the London Underground, he is to announce the details in a Commons statement this afternoon 25 Feb 1997 (credit:PA)
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A passer-by stops to look at Floral tributes as London's rush hour ground to a halt tonight (Tuesday) as commuters stopped to pay their respects to the 31 people who were killed in the King's Cross fire disaster 10 years ago. A minute's silence at 7pm across the capital's underground followed a brief service at King's Cross station attended by families of victims of the tragedy, and members of the London Fire Brigade and British Transport Police, and London Underground staff 18 Nov 1997 (credit:PA)
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Commuters travel past London's largest landscape painting along the wall of the Trav-o-lator (moving walkway) at Bank Underground Station in London after it was unveiled earlier today (Monday). The 282 foot, 1.5 million mural, which is American Airlines' latest advertising campaign, depicts a 5,000 mile East to West trip across the USA 26 Jan 1998 (credit:Neil Munns/PA )
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English former athlete and politician Sebastian Coe aboard a tube in the London Underground 28 Apr 1998 (credit:PA)
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Protestors sitting on top of an underground train Monday unfurl a banner at London's Bank Station after members of the Reclaim the Street Movement brought trains on the Central Line platform to a halt for 30 minutes 13/07/1998 (credit:Peter Jordan/mk)
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Covent Garden tube station is closed, as tube trains were cancelled and stations closed because of a strike on London Underground. A 48-hour walk-out by members of the Rail Maritime and Transport Union over job security led to 25 stations being closed. 16/07/02 : Talks aimed at averting a strike which will cause travel chaos for millions of passengers were being held with time running out for a breakthrough in a row over safety. Workers on London Underground are due to walk out for 24 hours from 8pm on Wednesday, which will cripple Tube services throughout Thursday. Leaders of the Rail Maritime and Transport union were meeting LU officials today in an 11th hour bid to avert the strike. (credit:PA)
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Transport Minister John Reid and Deputy Prime Minister John Prescott (R) travel on a tube train to open the first phase of London Underground Jubilee Line extension. Prescott took the 7-minute trip south from Stratford in East London to the Dome at Greenwich (credit:PA)
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Britain's Prime Minister Tony Blair travels on the newly built Jubilee Line extension on the London Underground, en route to the Millennium Dome in Greenwich 21 Dec 1999: (credit:PA)
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A woman traveller rides on an escalator in the renovated Westminster Underground station designed by Michael Hopkins & Partners architects, part of the London Underground Jubilee line extension 26 Jan 2000 (credit:PA)
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Lifelike models of actor Sean Connery and singer Kylie Minogue, on the platform of Baker Street London Underground station. *Research conducted by Madame Tussaud's reveals that visitors to London put the tube in the top three attractions in their visit to London. According to the results London's history, shopping and underground network are the highlights whereas the weather, food and prices are the low points. 16 Mar 2000 (credit:PA)
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A lifelike model of presenter Chris Evans is admired by a young boy, on the platform of Baker Street London Underground station. Research conducted by Madame Tussaud's reveals that visitors to London put the tube in the top three attractions in their visit to London. According to the results London's history, shopping and underground network are the highlights whereas the weather, food and prices are the low points 16 Mar 2000 (credit:PA)
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Police evacuate Westminster Underground Station in London after bomb disposal experts performed a controlled explosion on a suspect device found on a London tube line near Ealing station. * The security alert brought chaos to tens of thousands of rail travellers as commuter trains and services to and from the west of England, South Wales and the Heathrow Express which also travel through Ealing Broadway were hit 19 Jul 2000 (credit:PA)
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The London Underground train which was hit by a falling tree as it was travelling between Osterley and Boston Manor near Hounslow, south west London, after a night of hurricane winds and torrential rain 30 Oct 2000 (credit:PA)
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The scene outside White City Underground Station near the BBC Television Centre in Wood Lane, London, following an explosion which destroyed a taxi in the early hours of 04/03/01. Coded warnings were received by the police and bomb disposal teams attempted to carry out a controlled explosion when the bomb went off. (credit:PA)
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The emergency services arrive on the scene at Chancery Lane Underground Station in London after a tube train hit a tunnel wall 25 Jan 2003 (credit:PA)
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Justin Manser performs on the first day of licensed busking on the London Underground at Canary Wharf station, the first of 12 stations to host legal buskers across a total of 25 pitches from Dockalnds to the West End 19 May 2003 (credit:PA)
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The Oyster car pre-payment system was introduced in July 2003 (credit:Flickr betsyweber)
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A train on the DLR (Docklands Light Railway), in London 9 Apr 2004 (credit:PA)
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Sebastian Coe, chairman of the London 2012 Olympic bid, unveils a giant banner at the BT centre 14 Feb 2005 (credit:PA)
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14 dancers from the UK's Rambert Dance Company perform extracts from their 'Constant Speed' production on an escalator 17 Jan 2005 (credit:PA)
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Prime Minister Tony Blair (left) and Deputy John Prescott visit St. James's Underground Station in London to attend a meeting to signify their support for the tube Improvements 22 Jul 1999 (credit:PA)
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Escalators at Canning Town tube station, designed by architects Troughton McAslan, now open as part of the London Underground Jubilee line extension 11 Nov 1999 (credit:PA)
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Escalators in the Canary Wharf tube station, designed by architects Fosters and Partners, now open as part of the London Underground Jubilee line extension 11 Nov 1999 (credit:PA)
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Stratford tube station, designed by Troughton McAslan and Chris Wilkinson Architect, now open as part of the London Underground Jubilee line extension 12 Nov 1999 (credit:PA)
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Glass barriers on the platforms at Bermondsey tube station, designed by Ian Ritchie Architects, part of the London Underground Jubilee line extension. The barriers have been introduced to increase the speed of trains by reducing the flow of air through the tube tunnels 12 Nov 1999 (credit:PA)
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Britain's double Olympic champion Dame Kelly Holmes, second left, celebrates in London's Trafalgar Square, after London was awarded the 2012 Olympic Games, Wednesday July 6, 2005. Crowds in London cheered and waved flags as they heard Wednesday that their city had overtaken Paris to win the 2012 Olympics. The announcement by the International Olympic Committee in Singapore was shown on giant screen Trafalgar Square in central London, and in the east London area where the Olympic village will be built 06 Jul 2005 (credit:AP Photo/Sergio Dionisio)
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Injured tube passengers are escorted away from Edgware Road Tube Station in London following an explosion, Thursday July 7, 2005. An explosion destroyed a double-decker bus in central London during rush hour Thursday, police said. Two other blasts also went off in other buses, reports said. There were reports of casualties. The explosion near Russell Square occurred not long after blasts on London subways earlier Thursday, police said. Dow Jones Newswires reported that police confirmed explosions on at least two others buses. One of the buses exploded near Russell Square, police said. A witness said the entire top deck of that bus was destroyed 07 Jul 2005 (credit:AP Photo/Jane Mingay)
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In this image provided by commuter Alexander Chadwick, taken on his mobile phone camera, passengers are evacuated from an underground train in a tunnel near Kings Cross station in London, Thursday, July 7, 2005. At least 33 people were killed Thursday in three explosions in London's subway system, a senior police official said. Deputy Assistant Commissioner Brian Paddick said others died in an explosion on a bus in central London but gave no figures. The second blast, at 8:56 a.m. (0756GMT), in the King's Cross area of north London, killed 21, Paddick said. (credit:AP Photo/Alexander Chadwick)
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Flowers are left outside Kings Cross Station, as people pay their respects after the bombings. 09 Jul 2005 (credit:PA)
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Police and emergency services outside Oval Tube Station in London, Thursday, July 21, 2005 following reports of smoke and explosions, two weeks after a series of bombings targeted London's public transport system. Three London Underground stations were evacuated at midday Thursday. Police also were investigating a report of an incident on a bus in east London. (credit:SERGIO DIONISIO/AP/Press Association Images)
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Friends and members of the family of Jean Charles de Menezes mark the fourth anniversary of his death, by holding a one minute silence after they unveiled a memorial which they have helped to make and have requested be allowed to remain as the permanent memorial to him at the Stockwell Station in London, Wednesday July 22, 2009 . On 22nd July 2005, Jean Charles de Menezes the 27-year-old from Brazil, was shot and killed by police officers at Stockwell underground railway station as part of an anti-terrorism operation 22 Jul 2009 (credit:AP Photo/Lefteris Pitarakis)
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A boring machine to be used for drilling tunnels stands on the site as work starts at the Olympic Park site in Lower Lea Valley, London, the first milestone in the construction project for the London 2012 Olympic Games is to transfer powerlines into underground tunnels Thursday April, 6, 2006. The powerlines are to be placed in two underground tunnels, with 52 electricity power pylons being demolished along a six kilometre (3.5 mile) route 06 Apr 2006 (credit:AP Photo/Kirsty Wigglesworth)
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London Underground employees observe a minutes silence outside Russell Square tube station in London. Friday is the first anniversary of the day four suicide bombers attacked London's transit system killing 52 commuters and themselves by detonating explosive-laden backpacks on three subway trains and a London bus 7 July 2006. (credit:AP Photo/Simon Dawson)
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Revellers drink on a tube train, before the ban on drinking alcohol comes into force at midnight. Hundreds of revellers took to the London underground to give drinking alcohol on the Tube a send-off to remember. An alcohol ban, announced earlier this month by new London Mayor Boris Johnson, comes into effect on the Tube, London buses, Docklands Light Railway and tram services across the capital. Police arrested 17 people and closed six tube stations 31May 2008 (credit:PA)
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East London Line extension work in progress at Dalston Junction in London 29 Nov 2008 (credit:PA)
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A sign of the London underground system is seen partially covered by snow outside Westminster Station in London, Feb. 2, 2009. Heavy snowfall caused major disruption in the capital with all London buses suspended and a skeleton service on other transport links 02 Feb 2009 (credit:AP Photo/Akira Suemori)
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Mayor of London Boris Johnson unveils plans to keep London moving during the tube strike at London Bridge mainline station, Railway Approach London. He apologised today for "misery" heaped on the millions of commuters and tourists whose travel plans were thrown into chaos by the Tube strike. 11 June 2009. (credit:Anthony Devlin/PA Wire)
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Conservative leader David Cameron travels by tube on the Underground to the O2 Arena in London today where he launched his Tickets for Troops scheme encouraging promoters of music concerts and sporting events to give free tickets to soldiers 3 Nov 2009. (credit:Stefan Rousseau/PA Wire)
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Aldwych Underground station which was used as an air raid shelter during the Blitz in World War II Is Opened Up For Public Tours To Commemorate The Blitz. 23 Sep 2010 (credit:PA)
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Artist Elizabeth Hepworth brings her full-size easel to the tube, to capture the travelling public in oils and acrylics. She aims to explore the beauty in the everyday and feverishly paints passengers between stops. Hepworth, 21, has started work on the District and Piccadilly lines. Works from the Commuter Project will be shown at the We Are Arts gallery in Holborn next year. 30 Sep 2010 (credit:PA)
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A commuter reads a copy of a newspaper headlining the rescue of trapped Chilean miners at an underground station in central London, Wednesday, Oct. 13, 2010. Plane crashes, terror threats, oil spills, toxic leaks. The TV news diet is often dire, rarely joyous. And then there were the pictures Wednesday of brave, dignified miners who had been trapped beneath the ground for more than two months being brought to the surface, to breathe fresh air and to hug their loved-ones. Communications technology, including live video from within the mine, turned the entire world into a global village hoping for the safe release of men they did not know and would probably never meet (credit:AP Photo/Sang Tan)
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Volunteers from AOL UK at Oxford Circus getting ready to travel on the London Underground on behalf of breast cancer charity CoppaFeel! in a bid to raise awareness of the importance of checking your breasts regularly 31Mar 2011 (credit:David Parry/PA Wire)
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People dressed as zebras enjoy a smoke on the London Underground to promote the launch of the Zebra Electric Cigarette 23 Feb 2012 (credit:David Parry/PA Wire )
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The Prince of Wales drives a London Underground tube train built for the Metropolitan line during a visit to Bombardier Transportation, where he toured the facility and met members of the workforce at their factory in Derby.Picture date: Friday February 24, 2012. See PA story ROYAL Bombardier. Photo credit should read: Arthur Edwards/PA Wire (credit:PA)
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American Fans ride the London Underground during the London Olympics 09 Aug 2012 (credit:PA)
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Torchbearer and London Underground employee John Light carries the Olympic Flame onto an underground train at Wimbledon Station, London 24 Jul 2012 (credit:PA)
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A T-Rex joins London commuters at Charing Cross Station during their journey to work, to mark the launch of Primeval: New World. 04 Jan 2013 (credit:PA)