The ''A4'' class of Pacific locomotives, designed by Sir Nigel Gresley for the London & North Eastern Railway in the 1930s, was arguably the most distinctive and most famous type of steam locomotive built in Britain. Their streamlined design not only reflected the art deco and modernist style of the era but was also functional, enabling them to travel efficiently at high speeds. On 3 July 1938 the most famous locomotive in the class, Mallard, broke the world speed record for a steam locomotive, travelling at 126mph. This record has never been broken.A total of 35 of these beautiful locomotives were built from 1935-38. The first four were originally painted silver, included the word ''silver'' in their names, and were built to haul the glamorous new ''Silver Jubilee'' train from London and Newcastle. Their success led to a second batch being built from 1937-38, named after birds, LNER directors or British empire countries, for new streamlined services from London King''s Cross to Edinburgh and to Bradford/Leeds.Leading up to Mallard''s world-record run, the A4s broke several other speed records and the efficiency of Gresley''s elegant design ensured they continued in top link service into the BR era. particularly London-Edinburgh but also with distinction in later years on the hilly Glasgow-Aberdeen route.During the great withdrawal of steam in the 1960s, six members of the class were saved for posterity - Mallard, Sir Nigel Gresley, Bittern, Union of South Africa, Dwight. D. Eisenhower and Dominion of Canada. Two of them found homes in North America and in the five decades since they have continued to delight the public across the globe. In 2013, to mark the 75th anniversary of Mallard''s record breaking run, all the surviving A4s were gathered together in the UK for the first time since the 1960s and fittingly Bittern set a new world speed record of 93mph for a preserved steam locomotive. This book introduces the ''A4s'' with a history of their construction, design and service for over 30 years with the LNER and British Railways, and an account of the career of the six remaining A4s in preservation. The book is well illustrated throughout with photographs and diagrams.