A report into the power cut which caused travel chaos and cut electricity for almost one million people in England and Wales has been handed in to the energy watchdog, Ofgem.

The National Grid Electricity System Operator said it gave its interim technical report to Ofgem on Friday, with the anticipation of the findings being released next week.

The Government has also launched a review to examine what happened to cause the outage and what can be done to prevent a repeat.

It comes as media reports suggest that a lightning strike and wind farm fault may have helped trigger the August 9 blackout and that questions are being raised about the resilience of Britain’s energy and transport infrastructure.

UK power cuts
People walking in darkness at Clapham Junction station (Yui Mok/PA)

The National Grid, which described the suggestions as speculation, said it will not comment until Ofgem has had time to look over its report.

The power cut stopped traffic lights from working, plunged Newcastle Airport into darkness, affected Ipswich Hospital and caused huge disruption on the railways during last Friday night’s busy commute, after generation from a gas-fired plant and an offshore wind farm was lost.

Energy minister Kwasi Kwarteng said it is “extremely unlikely” there will be more power cuts like the one which affected much of the South East last week.

Speaking to BBC Radio 4’s Today programme, he said: “I think it is extremely unlikely that it’ll happen again.”

UK power cuts
People waiting outside King’s Cross station, London (Lewis Pennock/PA)

He added: “It was a once-in-a-10-year event and what happened was unacceptable, and the thing that concerned me particularly about last week was not the failure of the two generators in itself, but the knock-on effects.

“The fact that once those two generators, power stations, have failed, the commuters and many people across the South East were affected, and that is what I want to look at, that’s the resilience of the system that needs to be investigated.”

Mr Kwarteng said it would be “premature” to conclude what action is needed, but said the Government “will certainly be looking to improve the system”.

The Times reports that about 5% of national power supplies were removed when Hornsea One wind farm off the coast of Yorkshire and Little Barford gas-fired power plant in Cambridgeshire both suddenly reduced their electricity output last Friday, just before 5pm.

The Times reports that the gas plant and wind farm failed within seconds of each other after a routine lightning strike to the grid near Little Barford and the shortage supply worsened as an unusually fast drop in frequency on the grid saw a series of smaller plants automatically tripping off the system.

Supplies to parts of the local power grids were then automatically cut to try to reduce demand and local distribution networks also cut power to rail signalling stations, according to The Times.

The final detailed technical report to Ofgem by National Grid will be submitted by Friday September 6.