The train is a Watford motor train service. These trains worked mostly a shuttle service between Watford and Croxley Green, and Watford and Rickmansworth. The first carriage is 57ft x 9ft 0in composite trailer car no. 3726 of diagram M.11, which was turned out under account SX.257 on 21/07/14. This was an odd design, with hinged entrance doors in the vestibules, and gangways. The roof profile was also non-standard. It may have been an experimental forerunner of the Euston-Watford electric stock.

The rear carriage is 50ft 0in arc-roof third class driving-trailer no. 181 of Diagram M.59. This was of course a conversion from D.289.

These two carriages were together from 1918 until 1920, when no. 3726 was worked solo as Compo Motor Set 24. As such it was assigned to the Oldham/Stockport/Delph workings, and finished its days on the Delph branch in March 1955.

No. 181 was also loose from 1920, and in 1925/6 was paired with LMS no. 5590 (M.62) as Third Motor Set no.13. It lasted until 12/44.