"Oh," said my flatmate who knows all things. "That's a call sign, you know."
The sirens went off, and they swept us out of the station.
And then there was a very gentle boom.
We all screamed a little, like people on a slow rollercoaster, and then relaxed and smiled. Some of us giggled with relief. Whatever that was, it wasn't us.
Only when biking in, listening to Radio 5's brilliant coverage, did I realise I'd heard the bus bomb go off in Tavistock Square.
Tavistock Square is actually dedicated to peace. It's got a lovely garden with statues of peacemakers and pacifists.