Air-conditioned Tube train launched
The Tube's first air-conditioned train has started running - on a stretch of line entirely in the open air.
And although the new, cool trains will serve 40% of the Underground network over the next few years, there are no immediate plans for air-conditioned trains on the deep-lying, often boiling hot lines such as the Bakerloo, Northern and Piccadilly.
London Mayor Boris Johnson joined passengers on the first of the new trains on Monday which will run, to start with, on the Metropolitan line from Wembley Park to Watford.
Mr Johnson said: "Unless you are cycling, there cannot be a better way to criss-cross north-west London than in this smooth state-of-the-art addition to London's infrastructure. This train is quite literally the coolest ride in town."
A total of 191 air-conditioned trains - built by Bombardier Transportation in Derby - are being brought into service, with the roll-out on the Metropolitan line complete by the end of 2011.
They will start being delivered on the Circle and Hammersmith & City lines from 2011 and start operating on both lines from 2012. The District line will follow in 2013 and all trains will be on the network from 2015.
A Transport for London spokeswoman said: "Air-conditioning for the deep-lying lines is a long-term project.
"We are improving conditions on Victoria line trains but there is a lack of space for air-conditioning units on these deep-lying lines.
"We are looking at various solutions but you have to remember we are dealing with infrastructure which is very old."