Britain’s Foreign Secretary Philip Hammond will formally reopen the UK embassy in Tehran on Sunday, nearly four years after it was shut down.

The Iranian embassy in London will be reopened at the same time, as part of a rapid warming of relations between Iran and the west following the agreement reached on 14 July on the future of the Iranian nuclear program, the Guardian reported.

Hammond’s Tehran trip, the first by a British foreign secretary in nearly 12 years, comes soon after visits from the French and Italian foreign ministers, Germany’s vice-chancellor, and the EU’s foreign policy chief.

Hammond will be accompanied on his visit by a handful of British business leaders as well as the Foreign Office political director, Sir Simon Gass, who represented Britain in the marathon talks leading up to the July nuclear agreement.

He will meet the Iranian President Hassan Rouhani and other senior figures including the Iranian ministers of industries and business, petroleum and transport.

With an end to sanctions, foreign businesses are already queuing up to clinch contracts in Iran, which has vast oil and gas reserves.

Iran and Britain severed their diplomatic ties in November 2011. The British embassy was closed after hundreds of Iranian university students staged a protest, pulling down the UK flag and demanding the expulsion of the British ambassador.

Iran and Britain appointed non-resident chargés d’affaires in October 2013 as a first step toward resuming diplomatic ties