The reopening of Britain's embassy in Iran marks the start of an "exciting" new journey in diplomatic relations, the Foreign Secretary has said.
During a ceremony at the building in Tehran, Philip Hammond said the move would build trust between the two nations and insisted there should be "no limit" to what could be achieved in the future.
Britain has had no diplomatic presence in Tehran since a mob ransacked the British embassy in 2011.
The attack was a "low point" in relations but the election of Hassan Rouhani as president has seen links improve "step by step", Mr Hammond said.
In a ceremony at the embassy, where the the Union Flag was raised, Mr Hammond said: "Today's ceremony marks the end of one long journey, and the start of a new, and, I believe, exciting one."