@stux When I was at the university the local bicycle society had built a bike by welding two frames on top of each other and using a long chain between the pedals and the front gears. If you stopped at traffic lights you had to hold on to the traffic light pole to avoid falling over.
The queen came one day and there were police everywhere, so obviously someone rode the double-height bicycle through the cordon, into the building that the queen was in, did a loop around the lobby and back out again. For some reason it has very tall sliding automatic doors that allow this.
I think he'd planned to do some tricks or something, but one of the police officers was subtley signalling to him that if he wasn't going to leave promptly then they would probably have to tackle him or something.
Oh, and the bike was hot pink if I remember correctly.