Three former NatWest bankers charged with Enron-related fraud will be extradited to the United States on Thursday.
David Bermingham, Gary Mulgrew and Giles Darby will board a plane to the United States at Gatwick Airport at 9.30am to face trial over the alleged £11 million fraud.
The extradition of the socalled "NatWest Three" has attracted wide-spread criticism as it was sanctioned under a controversial fast-track procedure agreed with the US.
The treaty with Washington means Britons can be extradited to the US without evidence first being produced that they have a case to answer.
It has been bitterly attacked by Opposition parties because Congress has yet to ratify the treaty, which means there is no reciprocal arrangement for the extradition of US nationals to the UK.
The three men want to be tried in England because it is where they live and where the alleged offences took place.
They face custody when they get to the US unless they can raise a $1 million (£540,220) bail bond. The three men could be held in a US jail for two years awaiting trial.
On Sunday the Government launched a last-ditch bid to persuade the US Senate to ratify the Extradition Act 2003.
Home Secretary John Reid ordered Home Office Minister Baroness Scotland to fly to Washington in an attempt to persuade Congress that ratification is now essential.
It came as Opposition peers planned to amend the Act in the House of Lords to end the arrangement.
Writing in the Financial Times, Baroness Scotland urged the peers to delay until she had at least had the chance to make the case to the Americans.
"I want to have the opportunity to explain face to face our frustration at the Senate's delay without having to defend a spurious and wrong-headed amendment designed to score an anti-American party political point."
Attorney General Lord Goldsmith has already said there is "no basis" for looking again at the Serious Fraud Office's decision to leave the matter to the US authorities.
But the move was attacked by business leaders and Opposition parties who say the treaty is one-sided.
New director general of the CBI Richard Lambert said British business felt "terrific anger and terrific concern" over the case.
The three men deny an £11 million fraud in which their former employer NatWest was allegedly advised to sell part of an Enron company for less than it was worth.