Neil Woodford is the man who broke the deal. As the head of investment for Invesco Perpetual, Woodford oversees assets of more than £15 billion, largely holdings in energy, tobacco and other industrial stocks.

When chief executives or government officials in those sectors want to make a move, Woodford is key.

Woodford is arguably the best fund manager in the business, with an impressive track record stretching back 20 years.

Last night, as British Energy was putting the finishing touches to its deal with EDF, it called Woodford, as a matter of courtesy, to explain what was happening.

Devastatingly, Woodford said the deal no longer reflected the future costs of electricity and said he would not back it, sparking panic.

Fund managers in the City have a deserved reputation as a flock of sheep - they fol low each other, and controversy is to be avoided.

Woodford is different. Back when the internet boom was in full flood, he refused to buy into the s tory. He stuck to boring old companies that actually made profit and his performance sank.

The word went around - Woodford has blown it, he doesn't get the internet. "I can't invest on the theory that there will always be a greater fool than me out there," he retorted at the time.

When the dotcoms collapsed, investors remembered again why Woodford had earnt their trust in the first place.

The 48 year old is unusually unassuming for a man who holds such sway in the City. He could be flash, but he'd rather be polite. It is more than merely symbolic that Invesco's headquarters are out of town, far from the madding crowd, in Henley-on-Thames.

When Prudential, another major investor, agreed with his stance on the EDF deal, it was dead in the water.

To resurrect it, British Energy will need to get Woodford on side. The case they put will need to be watertight next time.