It was some two an a half years ago that Britain closed its embassy in Tehran after a protest against British sanctions turned violent.
In a written statement to parliament British Foreign Secretary William Hague said on Monday "the circumstances are right to reopen our embassy in Tehran."
It's a move Hague defended in parliament.
(SOUNDBITE) (English) BRITISH FOREIGN MINISTER, WILLIAM HAGUE, SAYING: (SOUNDBITE CONTINUES OVER SHOT OF MEMBER OF PARLIAMENT LOOKING ON)
"I can assure my honorable friend that there is no softening of any of our polices in relation to - in relation to - Iran. We look to Iran to see support for sectarian groups elsewhere in the Middle East, to reach a successful conclusion to nuclear negotiations, but I do believe it is important to discuss such issues with Iran, and we need the ability to do so."
Hague says Iran has a crucial role to play in the region, especially in Iraq and Syria.
(SOUNDBITE) (English) BRITISH FOREIGN MI