Isn't it possible to rally a few of the great unwashed from Brixton/Croydon/Tottenham to stage a repeat performance of their last lot of antics and storm the Iranian Embassy in London?
Look at the Iranian prime minister, and you will note that the great unwashed/unshaved/horribly dressed are Iranians!
On a more serious note: aren't embassies, particularly in "difficult" countries, supposed to be guarded by their own armed forces (e.g. US marines at US embassies)? What security is in force at UK embassies?