The BBC News website looks at the chequered history of British-Iranian ties in recent decades.
Britain is home to a vocal community of Iranian exiles
1951: The Iranian Government nationalises the Anglo-Iranian Oil Company, triggering a dispute with Britain.
1953: Iranian Prime Minister Mohammad Mossadeq is deposed in a coup backed by Britain and the US.
1979: Britain closes its embassy in Tehran following the Islamic revolution, and transfers its diplomats to a British interests section at the Swedish embassy.
30 April - 5 May, 1980: Six Iranian gunmen take over the Iranian embassy in London, taking 22 people hostage. The siege ends when British special forces storm the building. Five gunmen are killed and one is arrested. Nineteen hostages are set free but one dies and two are injured in cross-fire.
1988: The British embassy in Tehran reopens.
February 1989: Iran's Ayatollah Khomeini issues a religious edict (fatwa) ordering Muslims to kill British author Salman Rushdie, accused of blasphemy against Islam. Diplomatic ties with London are broken off.
September 1990: Relations are restored, but they are limited to the level of charge d'affaires.
May 1997: Mohammad Khatami, a reformer, becomes Iranian president, leading to efforts to normalise ties between the two countries.
September 1998: Relations with Britain are upgraded to ambassador level, after the Khatami government agrees to stop encouraging Muslims to carry out the death sentence against Salman Rushdie.
January 2000: Iranian Foreign Minister Kamal Kharrazi visits London.
September 2001: Jack Straw becomes the first UK foreign secretary to travel to Iran since 1979 - as part of efforts to forge a coalition against the Taleban in Afghanistan.
February 2002: Britain's improving relations with Iran suffer a major setback when Tehran rejects David Reddaway as London's new ambassador, calling him a spy.
June 2003: The UK urges Iran to open up its nuclear sites to tougher inspections, amid growing international concern that Tehran might be developing nuclear weapons.
21 August 2003: The UK authorities arrest Iranian diplomat Hade Soleimanpour, who is wanted by Argentina on terror charges, triggering a fresh row. Tehran demands the immediate release of Mr Soleimanpour and an apology from the British.
27 August 2003: Iranian Deputy Foreign Minister Ali Ahani travels to London to meet Jack Straw, who says the cannot interfere with a judicial matter. Tehran says it hopes the dispute will not come to the withdrawal of ambassadors, but adds that all legal and diplomatic options are open.
September 2003: Iran recalls its ambassador to London "for consultations" and shots are fired at the UK embassy in Tehran.
November 2003: Iran says it is suspending its uranium enrichment programme and will allow tougher UN inspections of its nuclear facilities, after mediation by foreign ministers from the UK, Germany and France.
May 2004: Regular demonstrations take place outside the UK's embassy in Tehran, with protesters criticising British and American troops for fighting near the Shia holy cities of Iraq.
18 June 2004: The UK, Germany and France draft a resolution for the UN nuclear watchdog, the IAEA, "deploring" Iran's lack of co-operation with inspections.
21 June 2004: Eight British sailors are held in Iran after their vessel apparently strays into Iranian waters near the border with Iraq. They are released three days later following negotiations between British diplomats and Iranian officials.
28 September 2005: Students in Iran throw stones and petrol bombs at the British embassy in Tehran in a protest over international attitudes to Iran's nuclear programme.
15 October 2005: Explosions in the south-west city of Ahwaz kill four people, prompting Iran to blame British intelligence operatives. The UK denies the claim.
25 January 2006: Iran says bombers who killed eight people in more bomb attacks in Ahwaz had links with British intelligence.
13 November 2006: UK Prime Minister Tony Blair insists in a speech that Britain's attitude towards Iran has not softened.
23 December 2006: The United Nations Security Council passes a resolution imposing sanctions on Iran over its nuclear programme, two months after the UK co-wrote a draft of the resolution.
23 March 2007: Fifteen British navy personnel are taken at gunpoint by Iranian forces in the Gulf off the coast of Iraq, the UK's Ministry of Defence says.