David Bermingham, Giles Darby and Gary Mulgrew, the three former Natwest bankers, have arrived in Houston to face charges in relation to the collapse of Enron in early 2001.

The three bankers will be asked to explain how $7.3m (£4m) went from Houston to the Cayman Islands, then into their personal bank accounts.

The link between Enron and Natwest relates to the former energy company established a series of off-balance sheet ventures to raise investment and hide losses.

NatWest invested in one of these, LJM Cayman.

The NatWest three, who worked in the bank's structured finance division, are accused of recommending NatWest sell its stake for $1m (£544,000) - allegedly for far less than it was worth.

The buyer was a partnership, Southampton LP, which made a huge gain shortly afterwards by selling the stake on.

The British trio, according to the FBI's indictment, were investors in Southampton LP along with Enron's global finance manager, Michael Kopper, who has since pleaded guilty to multiple money laundering and awaits sentence.

All three deny any wrongdoing.