A prisoner dubbed 'Britain's Pablo Escobar' killed a fellow convict during his time behind bars.
Curtis Warren is due to be released in a few months time, but he has spent much of his life locked up.
In 1999, while serving a 12-year sentence in the Netherlands after police seized an estimated £125 million worth of drugs and weapons, he kicked a fellow inmate to death.
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Turkish prisoner Cemal Guclu - who was serving a 20-year sentence for murder and attempted murder - allegedly started hurling unprovoked abuse at Warren in the yard of maximum security Nieuw Vosseveld jail, before throwing a punch.
Warren subsequently pushed Guclu to the ground, before kicking him in the head three or four times, killing him.
Warren said he was acting in self-defence, but a judge ruled he used excessive force and he was sentenced to a further four years for manslaughter.
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Warren was most recently sentenced to 13 years in prison in 2009, after being found guilty of conspiracy to smuggle cannabis.
The 59-year-old, from Toxteth, Liverpool, was the first gangster to be named on The Sunday Times Rich List, when he was reportedly bringing in £15 million a week.
His empire earned him an estimated £200 million fortune and he became Interpol's number one most wanted criminal, codenamed Target One.
The whereabouts of all this cash remains unknown.
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Labelling him 'Liverpool's most infamous gangster', the Liverpool Echo reports that prosecutors are wary of a 'murky network of hidden assets' through which he could access money made in the drug trafficking trade.
Warren insists he has no money left and has previously not paid a confiscation order that would have seen him leave prison years ago.
Back in 2013, prosecutors at Jersey's Royal Court laid out the scope of Warren's money laundering network.
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Then-attorney general Howard Sharp QC told the court that the operation included Swiss bank accounts, gold mining enterprises in Guyana and a property scheme in Turkey.
Warren was ordered to pay £198 million in a confiscation order or spend another decade behind bars, but he said he had no cash left and didn't pay the money, with his lawyer labelling a recording which the prosecution used for evidence as 'tittle-tattle, bragging and foolish talk'.
In the 2004 recordings - taken from his time in prison in the Netherlands - Warren could be heard discussing money laundering, stating he 'sometimes' laundered between £10 million and £15 million a week.
The Times reports he could have £1m cash bags stashed in gardens around Liverpool - though under the terms of his release he may not be allowed back into the city.
Jake Massey