M50455 entered service in the North West in 1957. The vehicle’s first allocation was shed 9A, Longsight depot, which at that time was receiving a number of new DMU sets that were being delivered as a result of the 1955 “Modernisation Plan”. The Class 104 3-car sets proved versatile replacements for previously steam hauled secondary & branch line services in the area, and M50455 would have worked many of the routes around Manchester, particularly the Manchester-Buxton line, which was to have an association with the Class for years to come. Stoke-on-Trent, Derby, Crewe, Birmingham and Manchester suburban route would also have been covered.

Around 1960, the short lived light green livery that M50455 was delivered in was replaced by the more conventional BR green that was to last much longer. M50455 continued to work around the North West routes it was designed for throughout the 1960’s & 1970’s. During this time, British Railways’ policy resulted in the vehicle losing its lined green livery in favour of all over blue. This was also the start of the BR’s DMU refurbishment program. Although Class 104’s were never selected for proper investment and full refurbishment (unlike other more common classes such as 101 & 108) most vehicles went through a major overhaul, which included the removal of the original asbestos insulation and front end changes which were to change the character of the vehicle, the two character headcode box under the centre window being plated over. The introduction of the TOPS classification system in the 1970’s also resulted in M50455 being renumbered M53455.

The 1980’s were to see M53455 transferred away from its North West home south to the London area, where it was operating the lines that had not been electrified. Working a poor area of the BR network during a time of underinvestment, added to the fact the vehicle was now thirty years old, took its toll and reliability of all the units left much to be desired. The vehicle was moved around several times paired with many different vehicles as maintenance dictated.

Luckily, M53455 was to see an extended period of service when it was one of eight DMBS vehicles selected for refurbishment for the newly created Network SouthEast, which wanted them for use on its Gospel Oak-Barking line. Three of these eight vehicles were to survive in preservation (53437, 53455 & 53479). It was overhauled for the last time at Doncaster works in 1988 and was unveiled with 53539 as set L702 in the garish red, blue & white striped “toothpaste” livery. M53455 also lost its "M" prefix when it was repainted. Towards the end of service, the vehicle would have been split and run in many hybrid formations with other classes of DMU, as it didn’t make much sense to keep the Network South East 104 sets together with there being two brake vans in a set.

In January 1992 the Gospel Oak-Barking service (that 53455 was dedicated to) was given over to Class 115 units, so the vehicle was transferred to the Reading area for about 6 months works on “Thames Line” duties, the brake van door receiving a large graphic advertising this. By this time the vehicle had been reformed into its final set, L730.

M50517 was selected as the vehicle on the CVR in best condition, and was selected for restoration first. However by 1999 (once external restoration of M50517 had come to a conclusion), it was recognised a brake vehicle would be required to run with M50517. After inspection of the two DMBS vehicles in storage, 53455 was regarded as the better of the two vehicles so 53455 was taken out of store in 1999 for restoration to commence. Please view the dedicated page for more information and a gallery detailling M50455's restoration.