Perry Wharrie, 48, of Loughton in Essex, was one of three men convicted of possession with intent to supply after trying to smuggle the drug into the Republic of Ireland.

The seizure was the largest in the history of the Irish state and Wharrie's sentence is the longest ever for a drug crime.

His jailing comes just over three years after he was released on licence in the UK after serving 18 years for the murder of PC Mason, who was shot dead during an armed raid in Hemel Hempstead in 1988.

The sentence was handed on down at the Circuit Criminal Court in Cork, which had heard the carefully planned import operation foundered when the wrong fuel was put in the smugglers' boat.

The inflatable boat capsized off the Cork coast and one of the defendants, Englishmen Martin Wanden of no fixed abode, was found 'drowning in a sea of cocaine', the judge said.

Wharrie and a third, Joe Daly from Bexley in Kent, were arrested near the scene having spent two days on the run without food.

All three had pleaded not guilty, claiming their presence in west Cork was a coincidence, but at the end of a trial last more than 40 days the jury returned unanimous guilty verdicts.

Wharrie and Wanden were jailed for 30 years and Daly was given 25 years.

Under the terms of his early release Wharrie was not to leave the UK without permission but he ignored the condition.

The drugs, with a purity rating of 75 per cent and an estimated street value of more than £780million, were seized a year ago.