The three former NatWest bankers sentenced to 37 months imprisonment for fraud offences relating to the collapse of Enron will all be behind bars in the US tomorrow after the last of the trio reports to a Californian jail.

David Bermingham, 45 is due to begin his sentence at The United States Penitentiary in Lompoc, California tomorrow morning.

His former colleagues Giles Darby, 45, and Gary Mulgrew, 46, have already started their jail terms at separate US prisons in Texas and Pennsylvania.

Attention will now focus on how quickly the three can return to the UK.

The plea-bargain they agreed with the US Department of Justice last November — in which each pleaded guilty to one count of wire fraud — included a stipulation that the US Government would support their request to serve the majority of their sentences in the UK.

However, the bankers’ hopes for a transfer could be frustrated or delayed because the Department of Justice, which oversaw the plea-bargain, is not responsible for overseas prisoner transfers.

These fall under a separate federal prisons department that considers cases individually. Lawyers for the three have promised to petition the authorities immediately but accept that they cannot say how long the process will take.

The three, former employees of Greenwich NatWest, were indicted on seven counts of wire fraud by US prosecutors in 2002.

After maintaining their innocence for five years, they eventually pleaded guilty to entering into a complex scheme with Andrew Fastow, Enron's chief financial officer, designed to defraud their employer of about $20 million. The plea-bargain included an agreement that the three would repay their share of the fraud, about $7.3 million.

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