We hope it's nothing serious, obviously, but according to Twitter something happened just after 8am EST (noon AEDT) today at Heathrow terminal five. Tweets are claiming armed police are evacuating the whole terminal. [Twitter]
UPDATE: Twitter user @MartinBrunt says, "Armed police in stand-off with man threatening to blow himself up at Terminal 5 Heathrow. Terminal evacuated."
UPDATE 2: Heathrow terminal five has been reopened.