In 1950, a range of full-fronted coach bodies named the 'Ambassador' was produced, but with the maximum permitted length for coaches increased to 30 ft and the maximum width to 8 ft, a series of new designs was prepared. Many were given names, such as the Roadmaster and Vega, all intended for use on specific chassis. The Roadmaster particularly was unlike anything Duple had previously produced, with its high, straight waistline and small windows. It earned the nickname 'Iron Duke' and was intended for underfloor engined chassis, hence the higher waistline. The Vega was intended for the new production model of the Bedford SB, and the bodywork featured a gently curving waistline typical of Duple.