Today, the British embassy in Iran was opened for the first time in four years, marking a pivotal moment in the trade relationship between the two countries.
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During a ceremony overseen by British foreign secretary Philip Hammond, the national anthem was played while the Union Jack was raised over the building in Tehran. It was closed in 2011 after protesters ransacked it in retaliation against economic sanctions.
"Today's ceremony marks the end of one phase in the relationship between our two countries and the start of a new one - one that I believe offers the promise of better," Hammond said.
In London, meanwhile, the Iranian embassy was re-opened after a similar period of closure. Prime Minister David Cameron had expelled Iranian diplomats from London following the 2011 protest.
A few weeks ago, a deal was reached between Iran and western nations over Iran's nuclear programme. The UK, among others, agreed to lift economic sanctions so long as Iran reduces its uranium enrichment to a level way below that required to develop a nuclear weapon.
Today's re-opening reflects the two countries' desire to cooperate following the deal. It also follows a general improvement in Iran's relations with other global powers since Hassan Rouhani became President in 2013.
"Last month's historic nuclear agreement was another milestone, and showed the power of diplomacy, conducted in an atmosphere of mutual respect, to solve shared challenges,” Hammond said.
Iran is, and will remain, an important country in a strategically important but volatile region. Maintaining dialogue around the world, even under difficult conditions, is critical.
A small group of UK business leaders also attended today's ceremony, in the hope of discussing future trade opportunities with Iran. The country has oil reserves the size of Russia's to tap into, and UK brands will once again be able to market their goods there.
Representatives from Energy, Royal Dutch Shell and mining services company Amec Foster Wheeler were among those present.
Hammond said there was “huge appetite” among UK businesses hoping to invest in Iran.
In the first instance, we will want to ensure that the nuclear agreement is a success, including by encouraging trade and investment once sanctions are lifted.