Although the LMS ‘Black Five’ was a huge success, Stanier’s successor George Ivatt made a number of experimental modifications which resulted in some unusual variants from 1947 onward. No. 44748 was the first of a batch of 20 built with Caprotti valve gear at Crewe Works. Under this arrangement, the locomotive’s valve gear was driven by a single shaft between the frames, connected to the locomotive’s leading axle with a bevel gear. The modifications resulted in an unusual appearance, with bulbous steam pipes, lower running plates with wheel splashers and a modified cab. 

Less obvious was a larger wheel spacing between the centre and rear driving wheels. New to Longsight shed, Manchester in February 1948, this locomotive carried the temporary identification M4748 before being allocated its BR number 44748. Other than a brief spell at Derby shed, it remained a Longsight engine and was withdrawn from there in September 1964 and scrapped by the end of the year.