Laundered cash from Britain’s largest gold bullion robbery was hidden with the help of an audacious plan hatched with advice from Mossack Fonseca’s co-founder.

More than 30 years after the infamous raid on the Brink’s-Mat depot near Heathrow, new information shows how the robbers’ main money launderer tried to cling on to some of the proceeds with the help of the Panamanian law firm at the centre of the largest ever leak of offshore data.

Faxes, memos and company filings from deep in the firm’s archives show how, in the late 1980s, Jürgen Mossack played a vital role in advising – unwittingly at first – fugitive money launderer Gordon Parry.

The 1983 dawn heist had involved masked gunmen terrifying security staff into giving up vault combination numbers by dousing their genitals in petrol and threatening to set them alight. The gang drove off with 3.5 tonnes of gold, worth £26m (almost £80m today), making it the highest value robbery in British history at the time.

Facebook Twitter Pinterest The Brink’s-Mat depot near Heathrow in 1983. Photograph: Daily Herald Archive/SSPL via Getty Images

The raid left Britain in shock and the ensuing exploits of those involved in the elaborate laundering process established the Brink’s-Mat robbery as one of the most notorious episodes in British gangland history.

More than two-thirds of the gold has never been recovered. Meanwhile, at least half a dozen killings – including the 1985 stabbing of an undercover police officer – have been connected to the band of criminals who battled among themselves for decades for control of the bullion.

Thirty years later leaked papers from Mossack Fonseca’s archives have revealed surprising details of how the money launderers sought to outwit police on their trail.

As early as 1986, Mossack had been tipped off that he was unwittingly acting as a director of a company that might be owned by those moving money for criminals involved in the heist. In an internal memo never intended to leave its Panamanian files, Mossack refers to the “famoso robo del depósito de Matt Brink en Londres”, and records how a well-meaning informant had telephoned to suggest Mossack should resign immediately from a front company the gangsters secretly controlled.

“The company itself has not behaved illegally,” Mossack noted, copying the memo to his partner, Ramón Fonseca. “But it could be that the company invested money through bank accounts and properties that was illegitimately sourced.” Despite the tipoff, Mossack did not resign immediately. Moreover, the lawyer became a trusted adviser to a Panamanian company controlled by Parry, the gang’s offshore launderer-in-chief, who went into hiding in Spain.

The Brink’s-Mat robbers and launderers included “Mad” Micky McAvoy, Brian “The Colonel” Robinson and Kenneth Noye, as well as Brian Reader, who at 76 was the ringleader in last year’s Hatton Garden heist, another record-breaking robbery. After the robbery, large amounts of bullion were crudely smelted by Noye and Reader at the former’s home in Kent before being sent to a scrap gold dealer, John “Goldfinger” Palmer, near Bath, for resmelting and onward sale into the bullion market in Sheffield.

This laundering chain rapidly generated millions in cash. At one point, extra deliveries of new £50 notes were made to a Barclays branch in Bristol to cope with increased demand for cash withdrawals. Much of the money found its way to Parry.

Facebook Twitter Pinterest A handcuffed figure, covered with a blanket, at Feltham magistrates court, London, on 8 December 1983. The unidentified figure is presumed to be Brian Robinson. Photograph: PA/EMPICS Sports Photo Agency

First records in the Mossack Fonseca file show inquiries being made by Centre Services, an offshore specialist firm in Jersey, about potential names for Panamanian companies in 1984, 12 months after the Heathrow raid. No details were given of the person on whose behalf the inquiries were being made.

A fax to Jersey regretted to say one of the preferred names, “Midas Inc” – seemingly a joke – was not available. The next day, the more discreet Feberion Inc was chosen. Under Parry’s direction, but unknown to Mossack Fonseca, millions of pounds were salted in Feberion and other front companies and bank accounts in secrecy jurisdictions such as Switzerland, Liechtenstein, Jersey and the Isle of Man. He is said to have laundered £10.7m, for which he would eventually be sentenced to 10 years behind bars.

There is nothing in the Panama Papers to suggest that, at this time, Mossack had any inkling as to who owned Feberion or what it was up to. He may not have heard Parry’s name at this stage, though he acted as director of the new front company and his law firm dealt with its local administrative requirements in Panama.

To complete the board, and add what appears to be another layer of secrecy, Centre Services recruited two further directors from the tiny neighbouring Channel island of Sark. These two directors promptly issued two Feberion bearer shares, to be held on behalf of their unnamed owners by Centre Services.

These shares give an ownership interest in a company to the person holding them in their hands. They are popular with money launderers and tax evaders – and have been outlawed in many countries in recent years.

Facebook Twitter Pinterest More than two-thirds of the gold stolen at Brink’s-Mat has never been recovered. Photograph: Sebastian Derungs/AFP/Getty Images

With funds washing through his offshore front companies, Parry believed the laundering process complete. The cleansed money could be returned to Britain to finance legitimate property deals, unidentifiable as the proceeds of crime. Using offshore firms, Parry arranged deals including the purchase of land in London’s fast-regenerating Docklands and some buildings formerly part of Cheltenham Ladies’ College.

Through one Jersey company he bought Kathleen Meacock, girlfriend of robbery ringleader McAvoy, a Kent farmhouse, where she settled with her two rottweilers, Brinks and Mat. Then, a short drive from Meacock’s home, Parry used Feberion to buy a £400,000 home for himself and his family. Gold-plated taps were installed in the bathrooms and more than £60,000 was spent on curtains for Crockham House, an isolated mock-Tudor mansion set in substantial grounds in the backroads of Kent, near Chartwell, Sir Winston Churchill’s former country residence.

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There is no suggestion that the sellers of Crockham House, or any other of the properties Parry arranged to buy, were aware of where the funds had come from.

By late 1986, the authorities were catching up with Parry. In cooperation with the Jersey authorities, the Metropolitan police froze papers held in the offices of Centre Services and took control of the two Feberion bearer shares. Bosses at the tiny Jersey company panicked and rang Panama. This was the tip-off call that is thought to have first linked Feberion to the Heathrow robbery in Mossack’s mind.

A few weeks later, police who called at Crockham House found Parry had fled. His prospects looked desperate, but he was not about to give up. Shortly afterwards, according to the Panamanian law firm’s files, an audacious plan to seize back control of Feberion from the Met was hatched.

Centre Services were no longer of use as company administrators. Parry appointed a firm from Panama to replace them. These new administrators would not be as easily spooked by the attentions of UK police. Mossack Fonseca, meanwhile, took the role of legal advisers.

Parry once again had a team to do his bidding, but he still had problems: the only two Feberion shares had slipped from his control and he had been forced into hiding.

Centre Services’s advice was clear: “I presumed that it would be inappropriate to hold a shareholders’ meeting ... because we do not have physical possession of the share certificates,” wrote a senior official in a fax to Panama. “The shares are now held by the Metropolitan police in London.”

And there was more bad news: “I do not know the present location of Mr Parry, nor do I know how he can be reached. The solicitor who formerly acted on behalf of Mr Parry ... is presently in custody at Wormwood Scrubs prison. He is charged with handling [Brink’s-Mat] money.”

But Parry and his Panamanian advisers were determined to find a way out. In 1987 they arranged for a fresh set of Feberion directors to be appointed, instructing them to issue 98 new shares, this time to Western Cross Inc – yet another front company controlled by Parry or his associates.

At a stroke, the Brink’s-Mat laundering supremo had massively diluted the value of the two original shares and taken his company back from under the noses of the Metropolitan police.

The bold manoeuvre was set out clearly in instructions from Mossack himself – by then acting as the main legal adviser to Feberion – in an internal memo to a colleague. “Since the only 2 shares ... are in the hands of the police in London, you may suggest ... the resignation of the existing directors, including mine, [is accepted] … and new directors [are appointed].

Facebook Twitter Pinterest Gordon Parry handcuffed at Heathrow airport in 1990. Photograph: Dennis Stone/Rex/Shutterstock

“New directors can then issue the remaining share certifs [sic] and call a general shareholder meeting at which the majority of shares would be duly represented if that should be necessary for any reason in the future.”

In 1990, after more than three years on the run, Parry was found by police outside Fuengirola on the Costa del Sol and brought back to Britain. He was formally arrested as he stepped off the plane at Heathrow, not far from the scene of the heist seven years earlier.

At his trial, the jury were told Parry had helped make the gold seemingly “vanish into thin air”. The laundering plot, prosecutors said, had been carried out with nerve and daring, and was “little short of brilliant”, inspiring a “grudging admiration”. The evidence against him, however, was overwhelming. Sentencing Parry to 10 years in jail, the judge said: “There has never been a more serious case of handling.” In Westminster, the case had helped galvanise policy-makers into drafting a new criminal offence of money laundering.

Facebook Twitter Pinterest Kenneth Noye, left, and Brian Reader. Composite: Kent Police/Metropolitan Police/PA

Back in Kent, Parry’s family – who have never been accused of money laundering – had continued to enjoy the run of Crockham House long after his conviction. Not until 1995 were Brink’s-Mat solicitors able to secure control of Feberion and arrange the sale of the property. The buyer was a woman called Irene Beaumont – Parry’s wife.

With Parry long since released from jail, the couple are believed to still live in the house today. They did not respond to a request for comment.

Mossack Fonseca told the Guardian: “The allegations you make related to the Brink’s-Mat situation are entirely false. At no time did we know about any connection between that robbery and the name Parry. We were and are in the business of selling companies, not running them or their affairs.

“The administration of [Feberion] was entirely the domain of Centre Services. The final owner of the company was never made known to [Mr Mossack]. Mr Mossack was never contacted by the authorities of any jurisdictions with regard to the Brink’s-Mat robbery. There was no point [Mossack Fonseca] reporting anything to any authority since the matter was already under investigation.”

Panama Papers reporting team: Juliette Garside, Luke Harding, Holly Watt, David Pegg, Helena Bengtsson, Simon Bowers, Owen Gibson and Nick Hopkins