I worked as a contractor for BA in 1999/2000 and was lucky enough to have the desk in the very south-east corner of the 10th floor of TBC. With a south runway 09 departure, the LHR-JFK Concorde service would be about level with the 10th floor as she came by TBC (building speed before increasing her rate of climb presumably). Everyone, everyday would stop what we were doing and watch her climb out.
For fun, on our coffee break, a colleague and I would have a look at the res system to see who was on board. The most frequent names we saw at that time in seat 1A and 1B were ... George Michael and Geri Halliwell!
Love this thread!