Police said a walker found the body on the ground

Police said they were treating the death in Chingford of Neil Coulbeck, who worked for the Royal Bank of Scotland until 2004, as "unexplained".

He had been interviewed by the FBI as a potential witness.

Three ex-workers of RBS subsidiary NatWest are being extradited to the US on Thursday to face fraud charges.

The extradition has sparked a political row, with opposition parties and human rights groups claiming the treaty under which they are being sent to the US is one-sided as the Americans are yet to ratify it.

'Highly regarded'

Prime Minister Tony Blair has rejected calls to renegotiate the extradition terms.

Mr Coulbeck's body was found in a park near Newgate Street, Chingford, on Tuesday.

Mr Coulbeck's wife had reported him missing last Thursday. Police have yet to formally identify the body, which was removed from the parkland on Wednesday afternoon.

One day when this is all over I'm going to be coming home to my wife and children and some poor guy is not

David Bermingham

Former NatWest banker

MPs protest at extradition Q&A: Extradition

Mr Coulbeck had worked at the Royal Bank of Scotland until 2004, most recently as head of group treasury, the bank confirmed.

"Neil was highly regarded by his colleagues here in RBS and was a respected, capable and hard working member of our senior management team."

The fraud case centres on a NatWest transaction under which it sold off part of its Enron unit.

RBS said: "There is no evidence that Mr Coulbeck was involved in the approval of the transaction under investigation.

"RBS has co-operated fully with all the appropriate authorities and made them fully aware of all the relevant facts in our possession."

The FBI said it would not comment while the case was ongoing.

'Appalling'

One of the so-called NatWest three, David Bermingham, said he had been "knocked sideways by the news" of Mr Coulbeck's death.

"It is awful, appalling. One day when this is all over I'm going to be coming home to my wife and children and some poor guy is not and my heart goes out to his wife and family," he said.

He described Mr Coulbeck as "a superstar, a thoroughly decent, honest professional guy and a very experienced banker".

The former NatWest executives deny any wrongdoing

Mr Coulbeck was among NatWest staff who made witness statements about the extradition, Mr Bermingham, of Goring, Berkshire, said.

"Neil's statement was no more than a page and a half saying who he was and his role," he said.

Fellow accused Giles Darby, speaking from his home in Lower Wraxall, Somerset, said he was "absolutely shocked" by the death.

"It's an utter tragedy. I'm struggling to take it in, really.

"Of course, my thoughts are now with Neil's family and friends."

In 2002, US prosecutors issued arrest warrants for the three men, accusing them of conspiring to defraud their employers and investors in energy giant Enron, which had collapsed a year earlier.

It is alleged that the three British bankers - Mr Bermingham, Gary Mulgrew and Mr Darby - advised their employer Greenwich NatWest to sell off its stake in an Enron unit at well below its market value.

MPs' protest

They then left the bank and purchased a $250,000 (£135,000) stake in the unit - which they sold on at a much higher price, making a profit of $7.3m (£3.9m).

They deny any wrongdoing.

Their extradition was debated by MPs in an emergency session of Commons on Wednesday.

After a three-hour debate they voted by a majority of 242 to adjourn the Commons early in symbolic protest at the government's extradition arrangements.

On Tuesday, peers had voted in favour of suspending extradition agreements with the US until the UK-US treaty had been ratified there.