When airports were young, and terminal buildings younger, there was an experiment with airport terminals being built in the centre of London.
Not next to the runways, obviously, but it was at the time thought wise to check in your luggage and do the necessary legals in the centre of town, then catch a dedicated bus to London Airport.
The earliest of these central terminals was at Waterloo station, which operated between 1953-57, but it was to be replaced with a giant of a terminal building, in Kensington.
This was the West London Air Terminal, and parts of it still exist, as a branch of Sainsburys.
As a terminal building — albeit a long way from the airport — it still offered all the facilities you would expect, from baggage check-in, the luggage carousel, passport control, and probably tax-free shopping.
They had managed to linger long enough though for a series of model buses to be made, including the trailer. They even appeared in a few films and TV shows of the time, showing off how advanced London is as a city.
What killed it off was in part the extension of the Piccadilly line to Heathrow two years earlier, in 1977, and changing expectations by the passengers themselves, who preferred to make their own way to the airport and check-in there.
And sadly, no more Routemaster buses with luggage trailers.