By 1972, he was making £50,000 with each shipment. By the end of the year he was approached by Hamilton McMillan of the Secret Intelligence Service (MI6), a friend from Oxford University, who recruited Marks to work for MI6 because of his connections in the hashish-producing countries of Lebanon, Pakistan and Afghanistan, for his ability to seduce women, and for his contacts with the IRA. The next year, Marks began exporting cannabis to the United States to The Brotherhood of Eternal Love, hiding the drugs in the music equipment of fictional British pop groups that were supposed to be touring the country; he further expanded his operations with other smugglers and other methods of trafficking, often using his Oxford connections. As McCann was in danger of being executed by the IRA should MI6 tip them off about his involvement in drugs, Marks then gave up the smuggling operation at Shannon airport.
Marks then connected Ernie Combs, member of The Brotherhood of Eternal Love, with John Denbigh, a man with connections in the hashish-producing nation of Nepal. With the help of the yakuza, large quantities of the drug would be exported to John F. Kennedy International Airport in the guise of air conditioning equipment, where Don Brown's mob (headed by Carmine Galante) would then take possession of the drugs. A 500 kg (1,100 lb) deal was set up and executed on 4 July 1975, leaving Marks a wealthy man. Other deals up to 750 kg (1,650 lb) followed, and Marks continued to live under assumed names in the United Kingdom. In 1976 he travelled to America, and set up a 1,000 kg (2,200 lb) deal between Combs and 'Lebanese Sam' – making himself £300,000 in the process; he continued to regularly set up deals between his various American and Far East connections. In need of a new identity after his alias of Anthony Tunnicliffe was compromised in a police sting, in 1978 he bought Donald Nice's passport.
Released in May 1982, though with most of his employees still in prison for the crime of which Marks had been acquitted, he spent the next year running a legitimate wine importing business but he continued to spend more money than he was making and the savings he made from drug smuggling in the 1970s began to dwindle. In 1983, McCann was still at large and his smuggling enterprise was flourishing; he offered Marks the chance to sell 250 kg (550 lb) of cannabis and Marks accepted. Dutch police confiscated the full shipment and arrested Mickey Williams, a member of the London underworld who had agreed to help Marks on the deal. Marks then travelled to the Far East to set up cannabis deals with Salim Malik, a Pakistani hashish exporter who he had met through Durrani (Durrani had since suffered a fatal heart attack) and Phil Sparrowhawk, an exporter from Bangkok; they would smuggle their product over to Ernie Combs in America. He also arranged a 500 kg (1,100 lb) deal with Mickey Williams, who had travelled to Bangkok after his release from prison in Amsterdam. Marks laundered his money through various fronts: a travel agency, a paper mill, a wine importers, a bulk water transportation company and a secretarial service.
In Florida, Judy pleaded guilty to her small part in the racket and was released, having already served some months in prison in Spain. The money Marks made from his smuggling operations was spent on legal fees. He refused to plea-bargain or to inform on his associates, gambling that he could again convince a jury that the authorities had got the wrong man. As the trial began in July 1990, Patrick Lane, his brother-in-law and fellow smuggler, wrote to Marks to inform him that he was going to testify against Marks in court to get a more lenient sentence himself. Marks still was confident of beating the DEA in court, but Ernie Combs also agreed to testify for the prosecution so as to secure the release of his wife, and Marks had little choice but to change his plea to guilty to racketeering charges. He was sentenced to 25 years in jail and given a $50,000 fine; though he had originally been sentenced to 15 years he was taken back into court after the judge realised he had misspoken and said that his 10 and 15-year sentences were to run consecutively and not, as he had originally stated, concurrently.
He also argued for the legalisation of cannabis in numerous television programmes in the United Kingdom. On 1 October 2010, he was interviewed on Ireland's The Late Late Show. The Dutch Cannabis Seedbank Sensi Seeds dedicated their strain Mr Nice G13 x Hash Plant to Marks for his advocacy work.
Marks held a series of book-readings into 2014. In these live events he regaled his audiences with tales of his smuggling days and his time in prison, as well as offered insight into drug production and the arguments for legalisation of cannabis.
McGrath, Nick (11 April 2016). "Howard Marks: 'My royalty cheques are lifesavers'". The Daily Telegraph. Retrieved 22 June 2016. https://www.telegraph.co.uk/finance/personalfinance/fameandfortune/10204886/Howard-Marks-My-royalty-cheques-are-lifesavers.html
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My dad, Mr Nice: life as the daughter of Britain’s best-known cannabis smuggler Published by The Guardian on 21 August 2021 https://www.theguardian.com/books/2021/aug/21/my-dad-mr-nice-amber-marks-howard-marks
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