Stupid me, I assumed there was a tiny clock driving the mechanism that was just geared up to trigger the bigger machinery. That instead looked like a regular clock scaled up to Big Ben size.
Also - those guys are insane. The "safety harness" was a wooden plank chair with some ropes dangling you over the abyss.
That was a TV presentor from a children's programme called Blue Peter.
If you think that looks dicey, search for the video of when another Blue Peter presenter,John Noakes, cleaned Nelsons Column in Trafalgar Square. Note the overhanging wooden ladder and the entire safety equipment was a pair of flared jeans and platform boots!
He also climbed the mast of HMS Ganges which is possibly even more heart stopping.
It's the camera crew that gets me. Peter Duncan has a bucket hanging down to lower his CoG, whereas the cameraman has a hefty shoulder mount making his balance more precarious.
Certainly scary enough for Hallowe'en.