Detectives are selling off an Olympic-sized equestrian centre after an epic 16-year battle to seize the assets of one of Ireland’s most notorious criminals.

Drug trafficker John Gilligan has been forced to hand over nearly €500,000 to British authorities.

The High Court has cleared the way for the Criminal Assets Bureau to proceed with an application to have an equestrian centre and other property belonging to convicted drugs dealer John Gilligan and other members of his family handed over to the State.

Convicted drugs dealer John Gilligan smiled and said: "Keep it clean" after he was jailed for five years by the Special Criminal Court today for threatening to kill two prison officers and their families.

Convicted drugs dealer John Gilligan told the Special Criminal Court today that a prison officer verbally abused him and told him: "I hope you do every day of 28 years'' after a row over the opening of prison tuck shop.

A prison officer denied at the Special Criminal Court today that he had pushed convicted drugs dealer John Gilligan and used abusive language during an incident at Portlaoise Prison last year.

The Special Criminal Court has ordered that convicted drugs dealer John Gilligan should pay more than €17m within a year after finding that he had benefited from importing 17,500 kilos of cannabis into the country over a two-year period.

The Special Criminal Court today fixed June 4 as the provisional date for the trial of convicted drugs dealer John Gilligan on charges of assaulting a prison officer.

The State's attempt to confiscate the assets of convicted drug dealer John Gilligan rests on the evidence of Assistant Garda Commissioner, Tony Hickey, the Special Criminal Court heard today. Mr Gilligan briefly interrupted the proceedings from the dock to tell the court he has "no money".