 At the time Edward Thompson succeeded Sir Nigel Gresley as Chief Mechanical Engineer of the LNER in April 1941, Darlington works was busy building Class V2 mixed traffic locomotives.Although the V2 class were competent and powerful locomotives, Thompson did not like this design as it required more servicing than his own mixed traffic B1 class 4-6-0.He also envisaged a time when the V2s would be replaced by his own design of 'Pacific' locomotives, but would not receive authority to build a new class during the war.