The UK’s first automated mainline train made its debut on a London track yesterday but unions warned they would oppose any move to dispose of drivers.

Some 150 people were on board the 9.46am Thameslink service from Peterborough to Horsham which made a historic switch from manual to computer control as it sped through the capital.

The rail company, possibly wary of alarming passengers following the recent death of a pedestrian in the US at the hands of a self-drive Uber car, did not announce the change, meaning most remained none the wiser.

Govia Thameslink Railway, Thameslink's parent company, later stressed the driver had remained in the cab at all times to carry out safety checks and close the doors at stations and would take full control of the trains outside central London.

It was the first time that self-drive “automatic train operation” (ATO) has been used on the mainline rail network, although such trains are in use on several London Underground tube lines.

Unions have urged caution on the project, warning they will not support any rollout beyond London and stressing that a driver must be retained on all services.