A Royal Marine from Northern Ireland has pleaded guilty to preparing a terrorist attack after having stashed explosives in hidden caches.

Ciaran Maxwell, 31, was arrested in Somerset last August over the discovery of two dissident republican arms dumps near Larne, County Antrim.

He was later found in possession of maps, plans and lists of potential targets for a terrorist attack, on top of bomb-making instructions and manuals used by terrorist organisations.

Images of an adapted Police Service of Northern Ireland (PSNI) pass card and a PSNI uniform were also discovered.

Maxwell pleaded guilty at the Old Bailey to assisting another to commit terrorist acts between January 2011 and August 2106 on Friday (3 February), as well as drugs and fraud charges.

Appearing in court via videolink from Woodhill Prison near Milton Keynes, Maxwell spoke only to confirm his name and enter guilty pleas. He was remanded in custody to be sentenced at a later date.

The father-of-one, who grew up in the predominantly Protestant Unionist town of Larne, joined the Royal Marines in 2010 and was based with 40 Commando in Somerset.

He used his cover as a British soldier – during which he served in Afghanistan – to aid Irish republican dissidents opposed to power-sharing in the north of Ireland.

According to the charge details, he had stashed explosives in purpose-built hides in England and Northern Ireland. He also bought chemicals and components to manufacture explosives, the court heard.

Maxwell was caught after police said they had uncovered terrorist hides in wooded areas in County Antrim, containing bomb-making parts. Another hide was discovered near the Royal Marine's home in Exminster, Devon.

Military grade anti-personnel mines discovered in the searched were traced back to the Royal Marines base in Somerset, where Maxwell was based.

Commander Dean Haydon, of the Met Police's Counter Terrorism Command, said:"This investigation resulted in a significant disruption and protected public safety by removing a large quantity of dangerous material from circulation."

Assistant Chief Constable Stephen Martin, of PSNI, added: "The arrest and charge of Ciaran Maxwell highlights the benefits of excellent collaborative working between the Police Service of Northern Ireland, the Metropolitan Police and other national partner agencies.

"Working together, we have disrupted the activity of a dangerous individual and removed a very significant threat."