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.
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.
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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.
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.
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.
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