Electricity supply will return to normal today following yesterday's countrywide blackouts, the National Grid said.

Hundreds of thousands of homes and businesses across London, Cheshire, Merseyside and East Anglia were affected between 11am and 1pm yesterday.

The blackouts occurred when the Sizewell B nuclear power station in Suffolk and the Longannet coal-fired power station in Fife both went off-line within minutes of each other.

In total, nine generating units across the country became unavailable.

Stuart Larque, spokesman for the National Grid, said: "We think it will be a case of business as usual. We have a very robust system in the UK. It rarely fails and that's why everybody is talking about it so much."

The blackouts were caused by the opposite of a power surge as the National Grid deactivated local stations to maintain the required 50hz frequency. When demand is greater than generation, the system fails.

Yesterday, the Government came under pressure from the largest independent energy consultancy, McKinnon & Clarke, to build new power stations or face further power cuts.

David Hunter, energy analyst at McKinnon & Clarke, said: "The Government's inability to make long-term energy security decisions over the last decade is coming home to roost.

"Since the 'dash for gas' in the 1990s, the lack of political will to make tough decisions has left Britain short of power."

* Meanwhile, Nuclear power firm British Energy reported a sharp fall in annual earnings today after two of its stations went offline last year.

The technical issues at Hartlepool and Heysham 1, following the emergence of wire corrosion problems within boiler units, meant total output for the financial year to March 31 was unchanged at 58.4 terawatt hours (TWh).

British Energy said the output figure masked a better overall operating performance, with progress in the management of small generation losses.

Underlying earnings were down to £882 million from £1.22 billion a year earlier, although this was a smaller decline than anticipated in the City.
The company, which operates eight nuclear power stations, said this month that it needed several weeks to consider a range of takeover proposals.

British Energy's attraction to bidders, such as France's EDF, lies in its existing sites and the role they may play in the proposed development of the next generation of nuclear power supply.

The company is evaluating all of its sites, with four priority locations for new build units being considered in the south of England - at Sizewell, Hinkley Point, Dungeness and Bradwell in Essex.