Two were inherited by the London and North Eastern Railway (LNER) at its formation in January 1923, and a third was purchased later.

The Great Eastern Railway (GER) bought a Simplex petrol locomotive from Motor Rail (works no.

[1] The NBR bought a Simplex petrol locomotive from Motor Rail (works no.

[2] Shortly after the grouping, the LNER gave the classification Z6 to the ex-NBR locomotive, and temporarily transferred it to Brentwood for trials, after which it was returned to Kelso in October 1923.

[4] The ex-NBR locomotive was subsequently tried at other locations, including Connah's Quay from June 1928, and Ware from August 1928.

[6] In the meantime a third Simplex petrol locomotive was bought by the LNER from Motor Rail.

8430 remained at Brentwood until its withdrawal in September 1956, during which time it was renumbered twice: to 8188 by the LNER in July 1946, and to 15098 by BR in May 1949.

[8] None of the LNER Class Y11 locomotives has been preserved but several similar ones have, including: Nottingham Transport Heritage Centre also has another Simplex numbered 15100.