A former IRA prisoner who tried to kill three policemen is now a “man of peace”, a court has heard.

Unfortunately, having changed from being a “dedicated participant in the struggles” to a “voice” calling for the violence to end, Ronald McCartney’s attempts to help a troubled friend had put him back in the dock on blackmail charges, his barrister said.

James Wood QC said that instead of “adopting a sensible approach”, his client made a “completely nuclear, cack-handed misjudgment” resulting in him being wrongly accused of attempting to extort money from two businessman.

He told Southwark Crown Court jurors they would not only have to consider his background, but decide whether McCartney was a “fighter or a peacemaker”.

The 55-year-old, of Ross Road, Belfast, and two co-defendants deny two counts of conspiracy to blackmail between January 1 and April 16, 2008.

In the dock with him are Nick Mullen (60), another former IRA prisoner, of Birlington Mews, West Acton, west London — who has decided not to give evidence — and Louis O’Hara (43), of Collard Avenue, Loughton, Essex.

The court has heard McCartney’s 1976 conviction for attempting to murder three policemen in Southampton saw him spend 21 years behind bars.

However, Mullen’s 30-year sentence in 1990 for being quartermaster for “an active IRA service unit” in London was later quashed on appeal.

The lawyer added: “Our case on behalf of Ronald McCartney is that he is in fact a man of peace.”

The trial was adjourned until today, when McCartney will resume his evidence.