In a signal of the most striking thaw in the Western ties with Iran for over a decade, Foreign Secretary Philip Hammond will reopen the British embassy in Tehran nearly four years since protesters ransacked the elegant ambassadorial residence and burned the Union Jack. The nuclear deal that the Islamic Republic struck with six major world powers last month has prompted a flurry of European visits - including from German and French ministers - aimed at positioning for the end of Iran's long economic isolation. But Britain has operated without an embassy since Iranian protesters stormed its two main diplomatic compounds in Tehran on Nov. 29, 2011. The protesters slashed portraits of British monarchs, torched a car and stole electronic equipment. Following the storming which Prime Minister David Cameron called a 'disgrace', Britain shut the embassy and expelled Iran's diplomats from London. Iran will simultaneously re-open its embassy in London on Sunday, Hammond said in a statement "Our relationship has improved since 2011," said Hammond, who will be only the second British foreign minister to visit Iran since the 1979 Islamic revolution that toppled the U.S.-backed shah. The last visit was by Jack Straw in 2003. "Four years on from an attack on the British Embassy, I am today re-opening it," Hammond said. The statement confirms an earlier report by Reuters on Thursday. The Tehran and London embassies will initially be run by chargé d'affaires but ambassadors will be agreed with months, Hammond said. Accompanying Hammond is a small group of business leaders, including representatives from Royal Dutch Shell, Energy and mining services company Amec Foster Wheeler and Scottish industrial engineering firm Weir Group.