BR & Paxman

The 'BR & Paxman' attribution in this encyclopedia identifies locomotive classes designed in a close partnership between British Railways and Davey Paxman & Co. of Colchester (latterly Paxman, within MAN Energy Solutions), a collaboration that produced some of the most technically advanced British diesel engines of the post-war era and supplied the power plants for several significant BR diesel classes.

Davey Paxman & Co. had a long history of manufacturing high-speed engines for marine, industrial, and railway applications before BR's diesel modernisation programme created demand for lightweight, high-output diesel engines suitable for railway traction. Paxman's Ventura and Y-series engines were used in various BR diesel locomotive applications in the 1950s and 1960s, and the company's engineering reputation made it a natural partner for BR's diesel development work.

The most significant collaboration was the Paxman Valenta engine, a 12-cylinder V-form diesel that powered the prototype High Speed Train power cars in their record-breaking 1973 trials and subsequently equipped the production InterCity 125 fleet. The Valenta's combination of high power output, relatively light weight, and compact dimensions made it ideal for the HST power car configuration, and the production Valenta-powered IC125s achieved the sustained 125 mph performance that transformed inter-city rail travel in Britain. Later the Paxman VP185 engine replaced the Valenta in some HST power cars during the fleet's extended life into the twenty-first century.