Class 125 Derby 3-car DMUs

Introduced: 1958
Coupling code: Orange Star
Underframe: 64ft 6in
Engines: Rolls Royce 238hp
Transmission: Hydraulic

Twenty of these hydraulic high density sets were built for use on the GE Lea Valley line from London Liverpool St. to Hertfordshire and Essex, serving the lines to Cheshunt, Epping and even as far east as Southminster on the Burnham-on-Crouch branch.

Their control system was unique, being based more on loco multiple working than other DMUs, with the engine speed being controlled by air pressure rather than electrically, and only one (larger) jumper cable per corner rather than two). This design was based on that trialed on 50000 / 56000, that set having a low density body rather than high density.

The large Rolls Royce engines allowed them the same performance as the EMUs with which they interworked between Hertford East/Bishops Stortford and Cheshunt. When the Lea Valley line was electrified the sets were transferred to Finsbury Park, working on peak-hour services out of Kings Cross alongside loco-hauled sets and the odd Cravens (the off-peak service was entirely Cravens to the end). This line was also soon electrified, resulting in their withdrawal by 1977 (before there was any interest in DMU preservation), none survive.