Anyway, he drew my attention to this snippet from The Fortean Times back in 2009 in an article about "floating platforms" in West Hampstead.
"The same, or a very similar, floating platform was seen again nearly 40 years later on the afternoon of 18 October 1955. The Reverend Pitt-Kethly was travelling on the Uxbridge train line to East Harrow, London. When the train had stopped at the West Hampstead viaduct, he noticed a reddish-brown and grey platform the size of a small bus. It was silent and travelled at a height of about 120ft (37m).Sounds like the reflection of the top deck of a double-decker bus to me. But what do I know. The only time I've seen a floating platform is while trying to change tube lines at Baker Street after far too many drinks.
There were approximately 20 helmeted men dressed in khaki uniforms standing on the platform, which moved at about 20mph (32km/h) and was in sight for three or four minutes. The Reverend did “not doubt the evidence of his own optics”."