After the Second World War, the Victorian Railways undertook a major rebuilding program known as "Operation Phoenix". One of the first tasks was the upgrading of passenger services on country branch lines, through the replacement of 23 wooden bodied railmotors built in the 1920s, and the withdrawal of steam locomotive hauled mixed trains.
An initial order of six 153 hp (110 kW) railcars, twelve 102 hp (80 kW) railcars and twelve 280 hp (210 kW) railcars from Walker Brothers in Wigan, England was placed, with twelve complete 280 hp (210 kW) units built in total, as well as a spare motor unit. The power units and controls were shipped out from England and the car bodies built locally by Martin & King in Malvern, with the finished units assembled at Newport Workshops. Each railmotor had a total seating capacity of 94.
The first of the 280 hp (210 kW) Walkers entered service on 6 June 1950, with 80RM departing Spencer Street for Daylesford. The railcars soon saw use on the Bendigo-Deniliquin and Ararat-Portland services, and by the time the 91RM was delivered, Mansfield, Wonthaggi, Woomelang and Wangaratta were also being served by the units. The long Glenrowan - Wangaratta section often saw the railcars exceed the 60 miles per hour (97 km/h) speed limit.
In later years the railcars' already poor riding qualities had deteriorated, especially due to their light construction. By the late 1970s the Walkers had reached the end of their lives, with a number of railcars being withdrawn from service during 1978 and 1979. By 1980 only 82RM, 85RM and 91RM remained in service. The last 280 hp Walker railmotor ran on 17 September 1980, with 82RM operating the 08.00 am service from Melbourne to Woodend and return. The intended life of the Walker railmotors was only 10 years. However, most were in service for up to 30 years.
In 1981 the Central Highlands Tourist Railway (now the Daylesford Spa Country Railway) acquired 91RM, 32RM and 56MT with the transfer being carried out in March 1982. Restoration of 91RM began in January 1987, and was certified for traffic in March 1990.