Signalling problems near Didcot Parkway which caused chaos for commuters this morning have now been fixed, say rail bosses.

Early trains between Didcot and London Paddington were cancelled and services from Oxford to London Paddington, Worcester and the North were also hit.

To make matters worse, First Great Western's supply of replacement buses was severely reduced due to the demands of race goers travelling to Ascot.

But Network Rail engineers have now fixed the problem and spokesman PJ Taylor said train services have now started running.

He added: "The technical problems were fixed at about 8.30am. There will still be some delays but we are hopeful that by mid-morning services will start running on time.

"At 5.40am, a power surge in the Swindon area knocked out signalling along the line and finding out why that happened will be the focus of our investigation."

From Oxford, the 7.57am to Worcester Foregate Street and the 8.06am to Birmingham New Street were cancelled.

First Great Western advised passengers not travel from Oxford or Didcot unless absolutely necessary until normal services resumed.

At Didcot Parkway, hundreds of passengers milled around, as all train services were affected and some commuters got back in their cars to travel to Reading to catch a train to London.

The 7.48am, 8am and 8.30am from Didcot to London Paddington were also cancelled.

Scott Johnson, 27, from the Ladygrove estate in Didcot, who works as a civil servant in central London, was caught up in the chaos.

He said: "I arrived at 6.20am to find that there were no trains anywhere - to London, Wales, Bristol or Oxford.

"I've got a meeting at 1pm today and I needed to get into the office early to prepare for it.

"This is an absolute piece of nonsense - maybe it is Network Rail's fault but First Great Western should have better back-up plans and I think they have been given enough chances.

"I suppose I could drive to Banbury and try to catch a train into Marylebone but my wife needs the car for her work."

Sue Evans, a spokesman for First Great Western, said: "We urged Network Rail to rectify the problems as soon as possible.

"Some Oxford passengers travelled to Banbury to take a Chiltern Railways service in London Marylebone, and their tickets are be valid on those trains.

"Ascot and the school run means an unusually high demand for the replacement buses we usually call on but we do now have buses running from Oxford, Didcot, Swindon and Reading. We apologise for the inconvenience."