Lunn ran a Sussex-based accountancy firm, Christopher Lunn & Co, whose 7,000-plus clients included many from the media and entertainment worlds.

The firm was investigated by HMRC in 2010 when the premises in Crowborough were searched and Lunn was arrested. HMRC uncovered evidence of a range of offences, which included the inflating of accountancy fees and the fraudulent use of trading losses, which the tax authorities said were intended to help Lunn and his clients avoid paying tax.

Lunn originally stood trial at Southwark Crown Court in September 2013, charged with six counts of cheating the Public Revenue. In January 2014, he was acquitted on two charges while the jury was unable to reach a verdict on the remaining four.

However, HMRC conducted a further detailed investigation, and Lunn was convicted at Southwark Crown Court in December 2015, where a jury found him guilty of four counts of cheating the Public Revenue.

Jennie Granger, director general, enforcement and compliance, HMRC said: ‘Lunn believed he could make up fraudulent claims to benefit both himself and his clients. Hard work from HMRC officers across the department proved him wrong. This long-running investigation has already recovered £20m as Lunn’s former clients settle their tax liabilities, with more to come.

‘I hope this result serves as a reminder to those who try to cheat the public purse – particularly those in the tax profession – that no one is above the law and that HMRC will relentlessly pursue tax evaders to bring them before the courts.’

HMRC has now started confiscation proceedings to strip Lunn of any financial gain he made as a result of his criminal activity.

As Lunn's clients were unaware of his actions, they have been offered a chance to put things right for themselves by paying any tax and interest due. HMRC said that any client who has not yet come forward pending the outcome of the trial should do so in order to bring their affairs up to date.

Civil investigations into Lunn’s clients have so far recovered more than £20m, with a projected £40m expected when all clients have settled.

Lunn's son, Christopher Jonathan Lunn (Jon), a former soldier who also worked at the firm but had no formal accountancy qualifications, was convicted in December 2014 on six counts under the Fraud Act, after he had sent false invoices to HMRC to try to cover up the fraud in the practice.

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