I visited in about 2003, while waiting to go to work. Rang the doorbell and asked if there was any chance of a quick visit. There was and I want to thank all concerned, but don't know any names, sorry. It was early afternoon and I think I watched a Concorde land amongst others. I was very impressed by the professionalism of all the controllers, alongside the 'Heath Robinson' style gizmo's - a combination which is so quintessentially British!
I also flew in and out of EGLL many times, and was very appreciative of all the controller's skills, which were and are the best in the world, in my opinion.
(I was the tw@t in pilot's uniform).
U