The last count was 1.2 billion passenger travelling on the various lines every year.
A postcard of a 1940s book cover with everybody carrying their gas masks in a sort of idealised blitz spirit kind of way, although perhaps reality was more like this
which looks rather more uncomfortable. The Aldwych* Station in 1940, one of 79 Tube stations used as air raid shelters
*UPDATE: By one of those strange coincidences of life I just noticed that one of my favourite bloggers has written about his recent visit down to the long closed Aldwych Station (pictured above) here (with pics and Doctor Who references).
An entry to ABC Wednesday, a journey through the alphabet this week sojourning at U