Mr Mills, the estranged husband of the Culture Secretary Tessa Jowell, was an adviser to Mr Berlusconi for many years and helped him set up shell companies in offshore tax havens.

The two men are charged with judicial corruption. It is alleged that in two trials in the 1990s Mr Mills helped Mr Berlusconi to escape justice by withholding details about the former Italian prime minister's media empire. Both men deny the charge. It is one of two connected corruption trials in which the men are charged.

The indictment sprang from a memo Mr Mills wrote to his accountant in 2004. Explaining the provenance of $600,000 which had come into his bank account from abroad, he said it came from "B's people" via Carlo Bernasconi, the head of the office of Mr Berlusconi's finance company, Fininvest, in Switzerland, who died in 2001.

He said it was in payment for evidence he gave in Italian courts during which "I turned some very tricky corners, to put it mildly" that "kept Mr B out of a great deal of trouble he would have been in had I said all I knew".

Italian prosecutors interviewed Mr Mills about the letter after they unearthed it. Mr Mills initially confirmed that the money had come from Mr Berlusconi, but later disavowed the confession, claiming that the questioning had induced him to make it. He told reporters that the letter to his accountant described a hypothetical situation as a way of soliciting tax advice for an unnamed client.

He has also made conflicting claims about the true provenance of the $600,000, mentioning a Neapolitan ship builder called Diego Attanasio. Mr Attanasio has denied being the source of the money.

Given Mr Mills's disavowal of his confession, the prosecution's hopes rely on documents detailing transactions between offshore accounts linked to Mr Mills. The corporate lawyer has claimed that he has proof of his innocence, which he will reveal at the right moment.

For his part Mr Berlusconi denies even knowing Mr Mills. When the case broke last year, just before Italy's general election, Mr Berlusconi said: "This English lawyer received $600,000 from a client and told his accountant that it came from a Mr B. He got this idea because he knew that the go-between [apparently a reference to Bernasconi] was dead. So this lawyer thought no one would ever deny it.

"When he realised the story was no longer within his office but had grown into something enormous, he should have told the truth."

The trial would appear to have the makings of a dramatic conflict. Unfortunately it is unlikely to live up to its billing. Defendants are not required to attend their trials in Italy. Mr Mills will not be flying in to Milan for the proceedings, and Mr Berlusconi is not expected to be there either.

In addition, under a statute of limitations law made more restrictive by Mr Berlusconi when he was in power, corruption cases must complete all judicial stages - trial, appeal, and final appeal - within 10 years of the alleged crime, or be abandoned. The deadline is February 2008, regarded as so close to impossible as to make no difference.