THE parents of a Taunton Royal Marine terrorist bomb-maker who infiltrated the British military have said they are horrified by his criminality.

Last month Ciaran Maxwell was jailed for 18 years at the Old Bailey for supplying bombs to dissident Irish republicans.

The former Royal Marine from Co Antrim stashed anti-personnel mines, mortars, ammunition and 14 pipe bombs - four of which were later used - in 43 purpose-built hides at eight locations in Northern Ireland and England.

His parents Teresa and John told broadcaster UTV's Up Close programme: "We utterly condemn what Ciaran has done. We are in deep shock and cannot comprehend it.

"We fully supported his decision to join the Royal Marines and were so proud when he achieved it.

"We have only known Ciaran as a loving son and a loving father who had a very bright future ahead of him. This makes what he did so difficult to understand.

"From an early age Ciaran was taught the difference between right and wrong and he crossed the line. The extent of his criminality is devastating and horrifying.

"We were completely in the dark about what Ciaran was doing and still ask ourselves why.

"Ciaran is our son but he is responsible for his own actions and he has been held accountable."

Bomb-making materials were found in barrels and buckets buried in the ground as well as an adapted Police Service of Northern Ireland (PSNI) pass card, a PSNI uniform and a police stab-proof vest.

The 31-year-old, who is originally from the port town of Larne and was with 40 Commando based at Norton Manor Camp in Taunton, Somerset, at the time of the offences, pleaded guilty to preparation of terrorist acts between January 2011 and August last year, possessing images of bank cards for fraud and possessing cannabis with intent to supply.

The Old Bailey heard that the father-of-one researched targets and discussed plans to attack police stations and officers.

His plot, however, was foiled when members of the public stumbled across his weapons' hides by chance.

DNA evidence found on parts of the haul led them to Maxwell, who was on the national database due to his alleged involvement in an unrelated assault case.

The judge said some of the ammonium nitrate recovered in Northern Ireland could have been used to make an explosive larger than "the notorious Enniskillen bomb", the Poppy Day bombing in 1987 which killed 11 people and injured 63 others.