The interior of a new Piccadilly train has been pictured for the first time ahead of the fleet’s planned introduction in 2025.

TfL says "rigorous" testing is under way on the trains, which will have new walk-through, air-conditioned carriages with wider doors.

The first of 94 new trains are being tested in Germany, with around half the fleet set to be built in the Siemens Mobility factory in Goole, East Yorkshire.

The trains are expected to be introduced on the Tube line from the start of 2025, replacing the current fleet, which dates back to the 1970s.

Ham & High: The new fleets is expected to enter service in 2025

From mid-2027, the frequency of trains at peak times will rise from 24 to 27 trains per hour.

This will ensure a train runs every two minutes and 15 seconds. Combined with the increase in the number of people each train can hold, the Piccadilly line should be able to increase its capacity at peak times by 23%.

In a post on X, TfL said: “The first trains are being put through rigorous testing on a test track and in a climate chamber with extreme weather conditions.”

Pictures showed outdoor and indoor testing of the new trains, as well as the interior of one of the carriages.

Siemens said that tests focused on the effects of temperatures ranging from -15C to 40C, extreme sun, ice, and wind speeds of up to 100km/h to check the train can still operate in extreme weather conditions.

The manufacturer added that monitors were used to understand what passengers would experience, measuring humidity and temperatures in the carriages.

Stuart Harvey, TfL’s chief capital officer, said: “Progress on bringing a new fleet of state-of-the-art Tube trains into service in 2025 on the Piccadilly line continues apace with rigorous testing now underway on all aspects of the train’s functionality and performance."

He added: "We want to follow the introduction of these new trains on the Piccadilly line by doing the same on the Bakerloo line, replacing the 51-year-old trains that it currently operates, and by continuing to modernise our fleets and signalling to make sure they remain safe and reliable."