Clive D. W. Feather wrote:
The advertising posters alongside the main escalator bank at
Tottenham
Court Road have all been replaced by flat screen displays, showing
adverts of course.

There's some advantage been taken - there was an advert involving
water
flowing down several screens - but I'm not convinced it's worth it.

I remember a TV-based advertising scheme on the Piccadilly westbound
(?)platform at Leicester Square, and also at Heathrow T4 platform -
don't think these lasted longer than a few years.

Also, the Paris Metro in the 1980's had something on a couple of dozen
platforms if I remember rightly - called 'Tube' I believe - that was
removed in the early 90's.

I don't know if the economics of this type of display has improved
enough for it to be financially viable long-term - it may well have
done, but durability is surely going to be an issue.