Bike theft is a problem in London, and 'lock inflation' has clearly taken hold. In 1979 you could use a cheap combination lock. In 1989 you needed a strong D-lock. In 1999 it was more like two D-locks.
In 2009, if this bike parked outside The Horse pub near Waterloo last night is anything to go by, you require two D-locks, a stockade and defensive moat.