At the start of the 1900s compound locomotives were very much in vogue. Development in the UK had made an uncertain start with the LNWR but in 1902 S W Johnson built the first two Midland compounds at Derby. These two largely experimental locomotives became the forerunners of a class standardised by the LMS in 1923. This volume, in the 'David & Charles Locomotive Monographs' series, is written by the famous railway historian & writer, O S Nock.