Two prototypes were completed in 1953, one with
Duple coach bodywork and one with
Park Royal bus bodywork. Production vehicles entered service from 1954. The last Reliance entered service in 1981. Following successive changes to Construction & Use regulations, the maximum length of the Reliance was increased twice from the original 30 feet: firstly, to permit an overall length of 36 feet from 1962; and later, to permit a length of 39 feet. Various AEC engines were fitted during the chassis's production, including the 7.7-litre AH470, 8.1-litre AH505, 9.6-litre AH590, 11.3-litre AH691 and 12.4-litre AH760. Transmissions fitted to the Reliance include an AEC
synchromesh gearbox, AEC
Monocontrol semi-automatic epicyclic transmission, and
ZF 6 speed crash-gearbox. The Reliance had the
Leyland Tiger Cub and, from 1959, the
Leyland Leopard as its major competitors throughout its life, even though they were built under the same ownership from 1962 onwards. After production of the Reliance ended, Leyland offered ZF synchromesh as an option for the Leopard, although the
Volvo B58 and other imported buses later won a number of customers' orders. ==Exports==