Transport for London (TfL) has revealed that London Underground’s new Piccadilly line trains will not start operating until the second half of 2026.

Since the first train was delivered to London, TfL engineering workers have been assessing the train, and have concluded that preparing it for testing and passenger service is more complex than had been previously thought. The tests have been rescheduled, which has caused the delay.

These new trains, most of which are being built in Yorkshire, will offer ten per cent more passenger capacity than the trains they will replace. They have walk-through air-conditioned carriages, wider double doorways, real-time digital displays and on-board CCTV. The trains are lighter than the current rolling stock, so run more smoothly and use 20 per cent less energy.

Engineers will test the interactions between the train and the infrastructure, which is some of the oldest on the Tube. In addition, the new trains will share infrastructure with other trains at some locations, which makes introducing it into a railway that is more than one hundred years old is even more complicated. TfL expects that issues will arise that will require time to address.

The Piccadilly line is more than 45 miles long, and connects central London with Heathrow airport, Uxbridge and Cockfosters. Its first section, between Piccadilly Circus and Finsbury Park, opened in 1906. The new trains will operate from the line’s two depots, at Northfields and Cockfosters.

The recent funding settlement from the Government will enable TfL to complete the introduction of the new trains on the Piccadilly line, and to progress discussions on new stock for the Bakerloo line.

“We’re proud and excited that these innovative new trains on the Piccadilly line will have a transformative effect for London. It will obviously be disappointing for customers that they will have to wait a bit longer for the new trains, and I regret that. But I would like to assure Londoners and visitors to our city that we are working extremely closely with Siemens to ensure that the new trains can be introduced as soon as possible in the second half of next year.”

Stuart Harvey, TfL’s Chief Capital Officer