Sadly if you know me by now, not only have I heard about it but actually bought a copy of the thing (travel edition natch) - although even I haven't played it yet.
On the instructions: "The object of the game is to visit four of London's places of interest and be the first to return to the main line station from where you set off. You travel by the Underground changing lines exactly as you would in real life".
Like real life there are inevitable hazards like "losing your ticket", "losing your camera", "missing your stop as your engrossed in a book", "getting stuck in the rush hour" etc etc. Stephen thanks for reminding me, would have been perfect to play at Xmas if I'd be suffering from tube withdrawal symptoms.
Ebay have a few of them. My travel copy wasn't from the 1970's although I think that's when it first came out.
The first item on Ebay (which will be sold in less than half an hour) was for a much older tube board game called LOBO which is apparently from the 1930's, when the underground was more reliable as there are none of the hazards we see in The London Game.