NEW trains have been taken out of service on the London to South Wales line following technical troubles.

The first service of the new Hitachi 800 train was cancelled on Monday due to problems with air conditioning.

The new electric trains which will run between South Wales and London made their first scheduled stop at Newport in Monday.

But GWR has withdrawn the trains temporarily for improvements to be made, with a spokesman saying the company to have them back in service "as soon as possible."

Trains in the £5.7 billion fleet will reach speeds of up to 125mph upon their initial roll-out. They are known as bi-mode trains, able to operate on electric and diesel.

The 10-carriage service London-Swansea service has 24 per cent more seating capacity than its predecessor, the High Speed Train, and will boast 40 per cent more seats.

The Hitachi 800 will enter service before electrification of the London to South Wales line is complete, due to its capacity for running on electric and diesel.

ion of the London to South Wales line is complete.