Battery-powered trains using a new rapid-charging system are being tested as part of a trial by Great Western Railway (GWR) the BBC has reported. 

The trains use the onboard FastCharge battery that delivers the equivalent of a full charge for a car in 85 seconds, and it is hoped they could help replace their diesel counterparts.

They are converted from old Underground trains and are being trialled in west London - but are expected to be eventually rolled out in the Thames Valley.

Simon Green, GWR's engineering director, described the more environmentally friendly trains as a "really good solution".

GWR's railway franchise includes the west and south west of England, as well as routes between London and Didcot, Oxford, Reading and Windsor.

Mr Green told the BBC: "The environment in this train is just as good as it is in the diesel train. Some might argue it’s slightly better.

"Therefore, from a passenger’s perspective... it takes you along that path of decarbonisation and it allows us ultimately to remove diesel trains from those services and that environment."

He said that "most customers and most neighbours of the railway" would be "really pleased" to see such changes.

The charging system is utilised before the trains head off on the return leg of their journeys.

It means the trains do not rely on a third rail or overhead wires, such as those on the Elizabeth line.

GWR has many similar carriages ready for conversion, including older Underground trains.