Britain faces regular blackouts and rising bills as electricity network cannot meet demand, experts warn

Lights were dimmed in millions of homes as seven generating units at other power stations broke down too.

Problems continued yesterday when the Hunterston nuclear power reactor in Scotland failed. That meant ten of British Energy's 16 nuclear generation units were out of service either for maintenance or through faults.

Sizewell B Nuclear Power Station shut down unexpectedly

The National Grid has refused to identify the power stations that shut down. However, they are understood to include two plants at Sizewell B in Suffolk

The power cuts affected parts of London, Cleveland, Merseyside, Cheshire, Lincolnshire and East Kent.

David Hunter, of energy consultants McKinnon & Clarke, warned of more problems.

'The power cuts of this week were caused by a series of coin-cidences,' he said. 'However, it seems likely that circumstances will conspire to mean this is more likely to happen again in the future.

'We have a problem of aging power stations, together with a lack on investment and a failure of political will to provide modern generating capacity.'

The next-day wholesale price for electricity has doubled in less than a year and bills for homes and businesses are soaring.

The power cuts began at 11.30am on Tuesday, when the two generating units at Sizewell B were shut down for technical reasons. British Energy, which owns the site, insisted the failure had nothing to do with the reactors and that there was no safety risk.

The National Grid control room in Berkshire was sent into chaos as systems failed on Wednesday

Separately, a coal-fired power station at Longannet, near Edinburgh, went off line because of technical problems. The unexpected failure of the three

plants within just two minutes suddenly removed 1,500 megawatts of generating capacity from the National Grid.

The fall triggered sub-stations at locations across the country to automatically cut out, stopping power to homes and businesses. The alternative was a possible meltdown.

David Porter, chief executive of the Association of Energy Producers, said: 'It was a huge coincidence. People were without power for 30 or 40 minutes I believe. Everybody in the industry is very sorry but it doesn't happen very often.'

He admitted that it may be difficult to ensure sufficient generating capacity in the summer maintenance period.

Tuesday's problems could have been worse had it not been for imports of French nuclear power. A cable under the Channel that carries 2,000 megawatts of electricity has been working at full capacity over the past two days.

Professor Dieter Helm, an energy expert at Oxford University, said: 'If you take that electricity out of the supply system, you would be in really serious trouble.'