A power cut is affecting large parts of the UK, including the south west, with rail services to and from London affected.

Western Power Distribution (WPD), the electricity distribution network operator for the south west, said there is a "major incident".

A WPD tweet said: "We are currently experiencing a major incident on the national electricity infrastructure. We are in the process of restoring customers now and will provide further updates as soon as possible for specific areas. We are sorry for the inconvenience this is causing."

A Network Rail spokeswoman said: "There was a power surge on the national grid this evening which means we lost power to all our signalling over a wide area, including the Newport, Gloucester, Ashford, Bristol, Eastbourne, Hastings, Three Bridges and Exeter areas.

"All trains were stopped while our back-up signalling system started up.

"While most of our signalling system has come back online and trains are running, there will be delays to journeys in these areas.

"Please check before you travel and thank you for your patience."

The Transport for London traffic news account said some traffic lights were out as a result of powercuts.

It tweeted: "Due to a large scale National Grid failure there is a power cut in the London and South East areas, meaning that some traffic lights are down. Please be very cautious on the roads."

In London, Thameslink tweeted: "Due to failure of the electricity supply, train services running across the whole network may be cancelled or delayed. More information to follow."

Rail operator Thameslink said many of its trains were "at a stand".

A tweet said: "The power network has failed in the large parts of London and the South East."

National Rail tweeted: "Power supply problems are currently causing disruption to a large number of train services. Information screens in some areas are also affected."

Passengers are being advised to check www.nationalrail.co.uk/service_disruptions/today.aspx for the latest updates.