Yesterday on the way home I stopped with my girlfriend by the Heathrow perimeter fence to watch the planes coming in to land. It was nice for a while, and then one of the planes made quite a late abortion of its landing. The next plane aborted as well. I then noticed that all of the planes on approach had turned away. Then I saw loads of fire engines speeding across the tarmac, as well as ambulances. They seemed to be heading to a group of parked BA planes. As well as the emergency vehicles inside the airport, many more (now including police) were coming from all around us to an entrance gate. All the outbound flights had also been canceled, and those who had aborted their approach were now landing on the other runway. Then I decided it was probably a good time to go. I'd love to know what was happening. I've looked on Google news several times, but not seen anything. We couldn't see any fire or smoke, so could it have been a drill/false alarm?