An American banking heir gave his lawyers "fake" e-mails purporting to show that his wife, the Jimmy Choo footwear boss, was hiding her wealth in an off-shore bank account, a court was told today.

Matthew Mellon's apparent attempt to taint the reputation of Tamara Mellon came after a bid to hack into her private affairs - which cost him a total of £11,750 - failed to find anything interesting or incriminating, Southwark Crown Court was told.

The multi-millionaire is alleged to have used Active Investigation Services (AIS), a firm run by two corrupt former London police officers, to snoop on his wife's computer files as they went through a bitter divorce.

However, after the hacking attempt failed to reap any dividends, one of the company's employees then created the bogus e-mails and sent them to her in order to expose any financial irregularities in her bank accounts.

When he was interviewed by the police after his arrest, the prosecution says Mr Mellon admitted he "believed" the documents had not been genuine, but he gave them to his solicitors anyway.

In the third day of her opening statement at the start of a two-month trial, Miranda Moore, QC, prosecuting, said the multi-millionaire started divorce proceedings in 2004 and the couple swiftly fell out over the settlement.

“Mr Mellon therefore, we say, engaged AIS to obtain information about his wife’s financial affairs because he was not getting it through the court process,” the prosecution said.

Police, who were already investigating the company, secretly filmed him meeting its co-owner Jeremy Young, 38, and David Carroll, 58, an agency employee, at his home to agree a £11,750 contract for the information he required, she added.

The court was told that a total of three “tempter” emails were sent to Mrs Mellon at work. If she opened any of the mails, the jury was informed, then a "Trojan" device would automatically attach itself to her computer and start spying on her.

One e-mail promised: “I have things on your soon-to-be ex-husband,” and then added “I think what he is trying to do to you is terrible.”

Another assured her: “Don’t think I am trying to get money from you. I am doing this because I think you are getting a raw deal from Matthew. I can help you put this guy in the trash if you want.”

However, the court was told that the Jimmy Choo boss became suspicious and asked David Barfield, her IT manager, to open them instead.

What resulted was almost no valuable information falling into the agency’s hands, leading Mark Caron, a US-based hacker who worked for the company, to try faking some e-mails instead.

“What he did eventually, a few months down the line, was to manufacture a couple of letters using names he had discovered that made it look that Mrs Mellon was not being frank with her financial disclosures," the court heard.

“He was able to do that with some credibility,” the barrister told jurors.

She said one of the hacker’s creations “appears to suggest that money had been sent by Mrs Mellon off-shore. In other words, putting it bluntly, she was hiding her assets.

“The other appears to show that she is selling the company, that contracts are on-going."

Mr Mellon, who is now divorced and living in Belgravia, central London, denies one count of conspiring to cause unauthorised modification of computer material between 1 July, 2004 and 4 February, 2005.

Also in the dock is ex-policeman Scott Gelsthorpe, 32, from Kettering, Northamptonshire, who helped run AIS, agency employee David Carroll, of Highgate, north London; Daniel Carroll, 36, from Westminster, central London; and Maurice Kennedy, 58, of Barnet, north London.

Mr Mellon's co-accused variously deny 15 counts of conspiracy, alleging fraud, the unauthorised modification and interception of computer material, and criminal damage.

Jeremy Young, a fellow ex-policeman and co-owner of the company, has pleaded guilty to a string of conspiracy charges. He was still serving in the Metropolitan Police when he set up AIS, the court was told.

Mr Mellon, who is heir to a £5 billionn oil and banking fortune, married Tamara Yeardye at Blenheim Palace in 2000.

The trial was adjourned until Monday.

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