The first Metrovick Co-Bo No.D5700 on display at the 30th August 1958 Works Open Day. Its official entry into service was 25th July, commencing trials and driver training on the Churnet Valley line in the following week. The showroom finish of a brand new locomotive sparkles in the summer sunshine, but unfortunately the shine wore off very quickly as problems emerged. By early 1960, the Class was suffering frequent mechanical failures, and just three of the twenty were available for traffic, with the others stored at Derby and Cricklewood. Many were declared unserviceable whilst BR and the manufacturers argued over who should pay to make the locomotives more reliable. Once BR and the locomotive builders eventually agreed on the necessary course of action, they began to be returned to Metropolitan Vickers' works at Dukinfield, Manchester to receive modifications to the troublesome Crossley diesel engines and a general overhaul. Nos.D5707 and D5713 were first and the rest followed two at a time with No.D5700 going there on 19th October 1961. It eventually emerged on 30th August 1962, having been transferred to Barrow on 3rd February. The modifications were to no avail because the Class was deemed non-standard under the 1967 British Railways Traction Plan. D5700 remained in service only until December 1967, outlived by the steam engines it was supposed to replace.