The BR modernization plan of 1955 envisaged the replacement of steam traction with diesel and electric locos by around 1975. Chief among the requirements was a loco more powerful than the 2000 hp locos that had been produced before then.

The Sulzer Company in Switzerland were able to provide an engine of 2300 hp, which was used in the Class 44. An uprated 2500 hp version was used in classes 45 and 46. 127 of these locos were built at Crewe and Derby between 1960 and 1962 but were overweight, and so a lighter co-design that would become Class 47 was developed using an uprated Sulzer engine producing 2750 hp. 512 of these were built between 1962 and 1966.

This book of mostly unpublished colour photographs by George Woods shows the locos in service from 1966 to 2019, working many different types of traffic throughout the BR system.