David Cameron and Iran's president will meet for the fist time in decades in New York later, as Britain bids to gain support from the hostile nation to join an international effort to tackle the Islamic State terror group, and to persuade him to drop support for the Assad regime.
The meeting with Hassan Rouhani, at a crucial United Nations summit, will be the first time a British prime minister has held face-to-face bilateral talks with an Iranian president since the country's Islamic revolution in 1979.
It comes just hours after the US, alongside five Arab nations, launched airstrikes against key Islamic State targets in Syria, stepping up the offensive to stop the terror group which has terrorised thousands, slaughtered minorities and beheaded three Western captives. Iran is an historic ally of Syria's President Bashar al-Assad.
Number 10 is said to be keen to focus British efforts against Islamic State on enlisting active support of regional powers in the Middle East. A Downing Street source told the Press Association: "We are under no illusion about the dangers of Iran's nuclear programme and our approach on that is not changing. However, if Iran is willing to join the international community to defeat Isil, then we will work with them on that but will be clear that you cannot take one approach in Baghdad and another in Damascus. You need a political solution in both if you are serious about defeating Isil."
Despite an earlier indication from Supreme Leader Ayatollah Ali Khamanei that he would reject any notion of an alliance with the US, Tehran's government continued to send signals over the weekend that it was keen to tackle the threat posed by Islamic State.
Iran is expected to take this opportunity to call for flexibility on its uranium enrichment programme, which previously sparked hardline sanctions by Western nations because of concerns such enrichment could give the country the capability of producing a nuclear weapon.
Cameron will later address the UN General Assembly and is set to use his speech to call for broad support for the new Iraqi premier Haider Abadi, and for efforts to tackle IS. The prime minister has thus far ruled out putting British soldiers' "boots on the ground" and it is unclear whether the UK will join the US and France in air strikes against Islamic State forces in Iraq or Syria.
Rouhani, widely hailed a moderniser when he came to office, has had his credibility in the West damaged by various high-profile human rights abuses and crackdowns by the Iranian police and judiciary.
And human rights campaigners are also using Rouhani's UN appearance to campaign on behalf of a young British-Iranian woman Ghoncheh Ghavami, currently imprisoned for attempting to watch a sports match. Iran bans women from entering stadiums if men are present.
How Relationship Between Iran And Britain Broke Down..
British-Iranian Relations
The 1953 coup(01 of06)
Open Image Modal1973 - Oil, again(02 of06)
Open Image ModalIran, the world's second-largest exporters of oil, are among the Organisation of Petrol Exporting Countires (OPEC, pictured) nations to announce an oil embargo, throwing many western economies, but particularly Britain, into crisis, as the price of oil surges.BP is one of the seven Western oil companies whose influence OPEC was set up to limit.The embargo is partly in response to Western support for Israel during the Yom Kippur War against Egypt and Syria. British bases were used to supply Israel with arms during the conflict.
The 1979 Revolution(03 of06)
Open Image ModalTwenty-six years after Britain played a key role in giving the Shah absolute power, things do not end well for the Iranian king and he is overthrown in a popular uprising, ushering in the Islamic Republic of Iran.Britain responds by closing its embassy in the country. Though it eventually re-opens in 1988, relations between the two countries remain frosty.
1980 to 1988 - The Iran Iraq War(04 of06)
Open Image ModalIraqi dictator Saddam Hussein (pictured) attacked Iran in 1980, leading to a war that lasted eight years and killed hundreds of thousands of people. Along with other Western countries, Britain backs Saddam. While officially neutral and observing an embargo on arms sales to either country, Britain covertly sold the Iraqis military equipment, as revealed by Cabinet papers published 30 years later. (credit:ASSOCIATED PRESS)
2007 - Royal Navy sailors taken prisoner(05 of06)
Open Image ModalIn the nadir of recent Iranian-UK relations, Iran seized 15 Royal Navy personnel, claiming they had strayed into their waters while searching a merchant ship.After just under two weeks in captivity, Iranian president Mahmoud Ahmadinejad announced they would be released and returned to Britain.On returning to Britain, the personnel claim the Iranians aggressively pointed machine guns at them, blindfolded them and held them in tiny cells.Iran responded: "Theatrical propaganda cannot conceal the mistake made by British military on violation of Iran's territorial waters and their repeated illegal entry into the country."
The ransacking of Britain's Tehran embassy(06 of06)
Open Image ModalBritain suspends diplomatic ties with Iran after protestors storm its embassy in Tehran and ransack it.The student protestors brought down the Union Jack flag and threw documents out of the window two days after Iran's parliament approved a bill that reduced diplomatic relations with Britain, following London's support of recently upgraded Western sanctions against Iran over its nuclear programme.
How Iran And The West Made Up
Ahmadinejad out, Rouhani in(01 of06)
Open Image ModalRouhani addresses the UN(02 of06)
Open Image ModalObama and Rouhani's historic phone call(03 of06)
Open Image ModalSeptember 28 2013 - A 15-minute phone call between Obama and Rouhani is hailed as a historic moment that ends the 34-year diplomatic freeze between the two countries.It is the first conversation between an American and Iranian leader since 1979.Rouhani tweeted about the conversation, saying Obama ended it by saying "goodbye" in Farsi.
Diplomats exchanged(04 of06)
Open Image ModalCameron calls Rouhani(05 of06)
Open Image ModalNovember 2013 - After Obama becomes the first American president to call the Iranian leader in 34 years, David Cameron calls him too, becoming the first prime minister to do so in more than a decade."The two leaders discussed the bilateral relationship between Britain and Iran welcoming the steps taken since President Rouhani took office," a Downing Street spokesman says."They agreed to continue efforts to improve the relationship on a step by step and reciprocal basis."Cameron also implores Rouhani to be "more transparent" with Iran's nuclear programme, Downing Street says.
About that embassy...(06 of06)
Open Image ModalSuddenly, being friends became a lot more urgent when ISIS took Mosul, Iraq's second city, and began tearing through the country executing opponents and imposing strict Islamic law on the population.The Sunni militants' rise has been blamed on the pro-Shia stance of Iraq's Malaki government.Under Saddam, the country's Sunni minority dominated political life and fought an eight-year with Iran, which is a Shia majority country and does not like the idea of a terrorist army on its doorstep.