Boltar wrote to uk.transport.london on Wed, 9 Feb 2005:

Call me a cynic but I can't help thinking that flip up seats are
probably a lot cheaper than the real thing though I'm sure this
in no way would influence their decision , no no, not at all.

They've had them on the Paris Metro since the year dot - certainly back
in the days of the old Sprague trains. I'm actually surprised they
haven't been introduced here until relatively recently. In the Metro,
there are great signs telling you not to use them during the rush hours
or when the train is busy, so that there is more room for standing
passengers.
--
"Mrs Redboots"
http://www.amsmyth.demon.co.uk/
Website updated 23 January 2005 with new photos