Senior royals and politicians have led tributes to the dead of the Battle of the Somme on the 100th anniversary of the bloodiest day in British military history.
Prime Minister David Cameron, French president Francois Hollande, the Prince of Wales, the Duchess of Cornwall, the Duke and Duchess of Cambridge and Prince Harry, led 10,000 guests gathered at the Thiepval Memorial to the Missing of the Somme that towers over the battlefield in France.
Ceremonies across the United Kingdom had earlier on Friday honoured the hundreds of thousands of victims of the brutal offensive which started in northern France on July 1 1916.
A two-minute silence ended at 7.30am, the time when the British, Commonwealth and French forces went "over the top" a century ago.
The British Army suffered almost 60,000 casualties on the first day alone and more than a million men would be killed or wounded on both sides over the course of the 141-day offensive.
Writing in the programme for Friday's commemoration in France, Prince Charles wrote that "their sacrifice and suffering will never be forgotten".
He added: "It is truly terrifying to imagine the destruction wrought across this landscape 100 years ago today. However, we now return to the battlefield in a spirit of reconciliation and respect.
"We honour the men who served from across Britain and Ireland, the Commonwealth and from France.
"We remember, too, the men from Germany who fought and fell in this most futile of conflicts. Their perseverance and courage when faced with such a monumental challenge are truly humbling."
Charles, Mr Cameron and Mr Hollande were among those who gave readings during the emotional Thiepval ceremony, alongside serving forces personnel and ex-England footballer Sol Campbell.
Game Of Thrones star Charles Dance, actress Joely Richardson and Harry Potter actor Jason Isaacs narrated events.
Other politicians present included Labour leader Jeremy Corbyn, Defence Secretary Michael Fallon, Scottish First Minister Nicola Sturgeon and Irish president Michael D Higgins.
The royals each wore a poppy and a cornflower brooch, called the "bleuet", which has the same symbolism of remembrance in France as the red flower does in Britain.
The brooches were made by French designer Catherine Desclaux and were worn by schoolchildren taking part in the ceremony.
British children laid wreaths at French graves and vice versa in the shared graveyard by the memorial.
Mr Hollande and Charles led the senior politicians and royals in laying wreaths at the Cross of Sacrifice, looking out onto the former battlefield.
On Friday morning in London, people lined Parliament Square where the roar of guns was followed by the two-minute reflection.
The King's Troop Royal Horse Artillery manned three sets of guns, drawn into place by horses, and fired every four seconds for 100 seconds.
In Edinburgh, a two-minute silence was held at Scotland's National War Memorial, with descendants of some of those who died at the Somme in attendance.
Mr Cameron laid a wreath at the cross, with a note reading: "Yours was the most horrific slaughter of a generation. We stand in awe of your sacrifice, determined that your legacy of liberty will live on forever."
Mr Corbyn laid a wreath at the Stone of Remembrance inside the memorial, with a note reading: "In memory of all who died; we resolve peace is the future."