They were allocated new to the LMR, spending most of their time at Chester. The first deliveries went to traffic in the Llandudno area, allocated to Llandudno Jct. The last four sets were transferred to the WR, and worked in the Cardiff and Reading areas. Although considered non-standard, their use of standard BUT equipment and blue square coupling code allowed them to operate with other classes.

They spent some time in the Watford area, working the St Albans and Belmont branches after the demise of the ACV/BUT railcars.

On the 8th May 1972 an oil train 'ran away' and crashed in Chester General station. M50407 and M56154 were in an adjacent platform and damaged beyond repair.