We had flights booked to go to Serbia for a music festival on 7/7/05, the day London was bombed!
I was supposed to meet my boyfriend (now fiance) at Liverpool Street Station and get the Stansted Express, but everything was closed and the mobile networks were jammed so he just walked up to my house on Hackney Road and turned up at the front door. We rang the airline (on the landline) to confirm our flight was still happening, so we wouldn't get any compensation if we missed it, even though all public transport to the airport and half the streets in London were closed!!
So we walked with our baggage, from Hackney Road, down Whitechapel High Street (past the hospital where all the Aldgate East victims were taken), past the giant mosque, past Aldgate East, tons of tv cameras, tons of police with helicoptors circling overhead. We made it to Fenchurch Street Station which was still open because it doesn't have a tube station in it (all tube stations were closed) and got one of the last trains out of London, getting out at Upminster to my boyfriend's parents house, where we had to borrow their car to drive to Stansted, and we made it to the checkin desk with a mere 5 minutes to spare!! Only to be told the flight was now delayed for an hour. ha.
We flew to Budapest just fine, and got the midnight train to Serbia, and were chatting to the Serbian people our age in our carriage - one of the girls said "oh why would you ever want to visit our bombed-out country?" then stopped herself, looked horrified considering London was just bombed and turned beet red! It really broke the ice and we had a brilliant holiday, all told, and followed the events in London on the hotel tv.