In 1965 the rest of Britain was buying front entrance Leyland Atlanteans and Daimler Fleetlines, while London Transport was still busy buying Routemasters. It occurred to the Executive that they ought at least try out these buses, especially if one man operation was to be the future. Staff shortages were already a significant problem, and the market forces approach - pay a decent wage to staff - was politically unacceptable. Londoners had to keep their cheap fares, and LT was not allowed to make a loss.

So London Transport bought a batch of 50 Leyland Atlanteans, and 8 Daimler Fleetlines, for extensive, intensive, trials, the XA Atlanteans in the City, and the XF Fleetlines in the Country Area.

LT specified a raised floor, with a step on the platform, in order to widen the constriction point between the wheel-arches, in an attempt to allow double-width entry/exit. To this end the staircase foot was also angled to the front. The bodies were based upon a design that Park Royal developed for Stockton Corporation.

The comparison trials came to an end, with not a few bangs and whimpers, during the autumn of 1969. The last XAs were removed from Stamford Hill and Tottenham in January 1970. New uses were sought for the XAs that would take them out of Central London onto less exacting duties. One person operation was also a consideration, and the buses were modified to accept fare machines or fare-boxes. XA22 became London's first double-decker omo bus on 22 November 1969, working on the 233 route from Croydon. The Peckham P3 operation should also have gone omo from the same date, but this was deferred until January 1970.

Meanwhile three XAs were officially transferred to the Country Area, taking over duties at East Grinstead from three XFs required for the Blue Arrow service at Stevenage. These three, XA46 - XA48, were transferred to London Country when the Country Area was nationalised in January 1970.

The class gathered again at Croydon (TC), where they were put to work on the West Croydon - New Addington C routes, including the express operations, for which they acquired blue blinds. Perhaps the longer runs suited them, but it must have been a hard bouncy ride into Croydon over the Shirley ridge for the commuters from the Dormitory on the Downs.

In 1973 their world changed dramatically. All fifty, including the London Country three, were sold to the China Motor Bus Company in Hong Kong for use on the cross-harbour tunnel route! They worked there until 1980, when they were replaced by ex-London Fleetlines: not the XFs, but their successors the DMS class.