As many passengers travel daily on London Underground as the rest of the British railway network in its entirety and passengers will be familiar with the differences between the Underground lines. What perhaps is less obvious to the travelling public is the difference between the sub-surface stock and the much smaller deep-level tube stock which is constrained by the size of the tunnels. Even within these two main types of stock there are differences between individual lines, depending on density of traffic in central London or the suburbs, special demands of servicing Heathrow airport (the Piccadilly Line) and even differing lengths of platforms. Stock on the Underground generally has a long life - the earliest sub-surface stock is the C stock from the 1970s and the earliest tube stock still in operation is the 1972 stock on the Bakerloo Line. The most recent is the 2009 stock on the Victoria Line stock and the S stock introduced on sub-surface lines from 2010. The introduction to the book gives a historical description of each of the main types of sub-surface stock and deep level tube stock in operation on the Underground today and is accompanied by detailed specifications of each type of stock and photographs. The book then provides a complete listing of the stock numbers of each vehicle operating on the Underground lines as well as battery locomotives and maintenance vehicles, with the listing grouped under the individual Underground lines, again accompanied by photographs.