Diplomatic staff from the Iranian embassy in London left Britain on Friday after being expelled following the storming of the British embassy in Tehran, the Foreign Office said.
"I can confirm that, earlier this afternoon, all diplomatic staff of the Iranian embassy in London took off from Heathrow airport," said a spokesman.
"They are returning to Iran in line with the foreign secretary's statement to parliament on Wednesday."
Foreign Secretary William Hague had given Iran's diplomats 48 hours to close their embassy and leave the country, following the storming of two British diplomatic compounds in Tehran on Tuesday.
Britain has also evacuated its diplomats from Iran and closed its embassy following the attacks, which Hague said could not have happened without the Iranian regime's tacit consent.