GREAT Western Railway's new intercity express trains carried their first paying passengers today.

The first electrically-capable trains, which are running on diesel engines until the completion of the electrification programme, entered service this morning taking passengers on the Great Western Main Line to London Paddington and west to Swansea.

Journalists onboard the service recorded the service reaching 125mph speed near Didcot Parkway, while drone footage captured by GWR saw one of the IETs overtake one of the old Intercity 125 services near Reading.

But the launch of the new trains did not go entirely without hitch.

Hitachi Rail's managing director Karen Boswell said: "I want to say to passengers that we're really sorry that the first service from Bristol didn't go as planned today.

"I was actually on that train this morning and the delay and the water leak meant that it was not the standard of service that we expect or are known for. We will do better and we apologise.

"We have taken the train back to the depot, we're investigating the issue, and will work hard to make it right for passengers.

"On a more positive note the first train from Paddington to Bristol did depart on time at 7 O'clock. It was a smooth journey that offered passengers more seats, space and faster wifi.

"More trains will follow until the full fleet of 57 trains are all in service next year."