Compounding was tried out by several British railways with no great success, but the ‘Smith Compound’ 4-4-0 introduced on the Midland Railway in 1902 by S Johnson was different and lasted in modified form for 50 years. The LMS added to the class which eventually numbered 240, one of which, no 1000, is preserved at the National Rail Museum.

This model in 5” gauge is by Mike Wheelwright and depicts no 2635 from 1903 as running from 1907, modified by S Deeley and with a six wheel tender and renumbered. Steam is supplied to a single high pressure cylinder located between the frames and which exhausts into a receiver before passing to the two outside low pressure cylinders.

Mike explained: “The main challenge is in the design and construction of the cylinders and motion. It is complicated by lying in three planes inclined at different angles with a crank and three sets of Stephenson link motion between the frames. The model has a miniature version of the Deeley double action regulator that enables it to start in semi-compound mode before changing over to full compound mode.”