The design was suitable for driver-only operation which helped bus operators to relieve the problems of labour shortages and costs, and became one of the alternatives to the traditional British double-deck buses (operated by a driver and conductor, such as the London Routemaster or Bristol Lodekka), as British legislation prevented driver-only operation of double-deck buses until the late 1960s.
The largest fleet was operated by London Transport and London Country, with over 1500 in total delivered between 1966 and 1972. Bodywork was supplied by Park Royal Vehicles, Metro Cammell Weymann and Marshall of Cambridge, to basically the same design.
The fleet was made up of a number of variations. The Longer 36' versions were referred to as Merlins, and divided into MB (single or dual door), MBS (dual door), and MBA (dual door with turnstile payment for use on Red Arrow services) classes.
The shorter 33' versions were known as Swifts. There were three variants of this model upon delivery. In the central area SM (single door saloon) and SMS (dual door with automatic fare collection) classes were painted red. London Country operated green SM-class dual door, fully seated saloons that had been ordered by London Transport. Subsequently, London Transport converted a number of SMS vehicles to conventional one-man operated saloons by adding more seats and locking the centre exit out of use. These were renamed the SMD class, but retained their original fleet number. Neither LT nor LCBS considered either design to be a success and the first examples were withdrawn and sold, many for scrap, in 1972, after just 4 years service. Most had been replaced by 1981 mainly by Leyland Nationals and MCW Metrobuses.
A much larger fleet of ex-LT buses were sold for service in Malta where they lasted - often rebuilt and re-engined until 2011. Some were taken by the Government Education department and remained in their London form apart from a new coat of paint. They were replaced by bendi-buses from London which had also had a very short life in the capital.
Other operators in the UK
AEC Swifts were also sold to several other operators. Over 100 were sold to Leeds City Transport, transferring to West Yorkshire PTE on its formation in 1974. Birmingham City Transport and Sunderland Corporation took smaller numbers of Swifts.
Great Yarmouth Transport bought eight Swifts new in 1973; these continued in service until the late 1990s, and were the last Swifts to run in service with their original operator. Three Swifts delivered to Morecambe Corporation in 1970 carried rare Northern Counties bodywork.
Following withdrawal from service with their initial operators, many Swifts were sold on for further use. Staffordshire-based independent Knotty Bus ran a fleet of four Swifts between 1988 and 1995. A small number of former London Transport Swifts ran for a time with Hants & Sussex (now Emsworth & District) on services in south east Hampshire.
British Airways once owned an AEC Swift, with a special body that had an open platform at the front, which was designed for airside duties.
AEC Swifts were also sold for the export market, and many were sold abroad after withdrawal. 65 Swifts with bodywork by local builder Bus Bodies were sold to South African operator Durban Transport in 1974. A number of AEC Swifts have been exported for use in Australia. Several former London Transport vehicles were sold to Maltese operators following withdrawal.
177 Swifts and Merlins were bought by Northern Irish operator Citybus between 1977 and 1980 to replace buses destroyed during the Troubles, although most were withdrawn after 1981. In early 1981 ten Swifts recently withdrawn by London Transport were exported to Italy to act as emergency control centres and shelters in the aftermath of the 1980 Irpinia earthquake.