I got to Hammersmith in plenty of time for the Open Tech conference on Saturday and I had about three quarters of an hour to kill so I was mooching around the Hammersmith Broadway shopping centre that is built over the tube station.
At about half past ten a general alarm went off and an insistent repeating taped message said that all staff and customers were to evacuate at once. I imagine that after 7/7 and 21/7 there was only one thought in most peoples' minds, but I was still astonished to see a minority of the public very close to panic bolting for the doors.
For some reason I had a strong feeling that it was very, very important not to run, but to walk almost casually out. I realise that this is somewhat ridiculous as well but it arrived in my head in an instant as a firm conviction.