This post, 12 April 2021, describes a vertical format, 400-piece jigsaw from Sovereign Publications, (although labelled as 600 pieces).
The Bill Sharman photograph features the famous Sir Nigel Gresley locomotive class 'A1', later class 'A3' 4-6-2, No.4472
Flying Scotsman, in LNER apple green livery. No.4472 is heading a 'Special' - 'The Flying Scotsman'. The picture looks as if it was taken when the engine was heading a 'Heritage Railway Special' or a Main Line 'Special. Go to the post of 28 June 2011 for a description of the two different identities - locomotive and train. The title of the jigsaw is
LNER Class 'A3' Flying Scotsman.