Simultaneously Park Royal bowed to pressure from the British Electric Traction (BET) group of major regional bus operators and replaced their rather elegant mid-1950s aluminium-framed body with a steel-framed structure of very angular outline, this first appeared as the production version of the integral AEC Bridgemaster, but soon spread to all other steel-framed Park Royal and Roe double deckers.
Simultaneously, in response to pressure from British Electric Traction (BET), Park Royal updated their buses by replacing aluminium-bodied models with a steel frame featuring an angular design. This initial version was the production model of the AEC Bridgemaster, but it quickly became standard on all steel-framed Park Royal and Roe double deckers.