Here’s a brief CNN report on the events. Many thanks to Vlad Tepes for uploading this video:
Interestingly enough, the Iranian government initially said that six hostages had been taken at the embassy, but that report was quickly withdrawn. According to Reuters:
Iranian Protesters Storm British Embassy
(Reuters) - Iranian protesters stormed two British Embassy compounds in Tehran Tuesday, smashing windows, hurling petrol bombs and burning the British flag in a protest against sanctions imposed by Britain, live Iranian television showed.
Iran’s semi-official Mehr news agency said protesters took six British diplomatic staff hostage from an embassy compound in the north of the city but it withdrew the story from its website minutes later without giving any explanation.
The attacks followed the rapid approval by Iran’s Guardian Council of a parliamentary bill compelling the government to expel the British ambassador in retaliation for the sanctions. A lawmaker had also warned Sunday that angry Iranians could storm the British Embassy as they did the U.S. mission in 1979.
Several dozen protesters broke away from a crowd of a few hundred protesters outside the main embassy compound in downtown Tehran, scaled the embassy gates and went inside.
Protesters pulled down the British flag, burned it, and put up the Iranian flag, Iranian news agencies and news pictures showed. Inside, the demonstrators threw stones and petrol bombs. One waved a framed picture of Queen Elizabeth, state TV showed.
Others carried the royal crest out through the embassy gate as police stood by, pictures carried by the official Fars news agency showed.