Although already a proven performer in the United States and elswhere ,the 4-6-2,or Pcific,did not gain prominence as a powerful express passenger locomotive in Britain untill 1922.As early as 1908,theGreat Western Railway had introduced itsGreat Bear Pacific,but weight restrictions precluded it's use on ant route except the London-Bristol main line and the enginewas rebuilt as Castle 4-6-0 LNER Chief Mechanicengineer Sir Ngel Gresley desighned the three -cylinder A3(originaly-A1 4-6-2 including the World Famouse Flying Scotsman.The engines of this class worked principally on the East Coast main line until dieselization began to thin their ranks in 1960-61.
An improved streamlined version of the A3 apperad in 1935 to haul the new high speed Silver Jubilee and Corionation express in 1938 no 4468 Mallard reached 126 mph the highest speed ever recorded for a steam locomotive no 4498 was named for its desighn ,Mallard was with drawn from service in 1962 and was exibited at Clapham untill the National Railway Musem was established at York ,Sir NgelGresley s[pent the last years of it's British Railway career in Scotland and was not taken out of service until1966
