Have you tried approaching the LT museum in Covent Garden?

They're very approachable. I asked them a while back about a spiral-
escalator that I saw as little more than a footnote in my various texts,
and they had some background research and directions to the site where the
few remaining parts existed by the time I was done getting the kids'
station-card punched throughout the exhibit. Great people.

--
http://mattdrury.net/travel (since 1984)