A Royal Marine with links to dissident republicanism made 14 pipe bombs – four of which were used in Northern Ireland, a court has heard.
A court hearing to decide how long Ciarán Maxwell will serve in prison is under way at the Old Bailey.
In February, Maxwell, 31, admitted a number of offences, including bomb-making and storing stolen military weapons.
The County Antrim man also pleaded guilty to drugs and fraud charges.
The hearing is expected to take up to three days.
On Wednesday, it was told that Maxwell had created “to-do lists” mentioning “targets, dummy runs and recces”.
The exact details were redacted by the court, but the targets included a Territorial Army centre and substations. There was also reference to a loyalist group and the need to notify news agencies.
In one of his hides, Maxwell placed a torch modified to be a booby-trap which when armed would explode if turned on.
Maxwell lived in Exminster, County Devon, and was based with 40 Commando in Taunton, Somerset.
He was arrested last August and a search near Exeter found hides with a range of explosive substances, as well as ammunition, weapons and tools for making bombs.
On Wednesday, prosecutor Richard Whittam QC told the court: “Across 14 of the locations involved in the investigation, Mr Maxwell had in his possession, or had constructed, 14 pipe bombs… Four have been deployed in Northern Ireland.”
The court heard dissident republicans have carried out more than 160 terrorist attacks since 2010, involving tactics including the deployment of improvised explosive devices (IEDs) such as pipe bombs.
Mr Whittam said: “Whilst attacks are mainly directed at members of the police, military and prison service, the nature of the attacks leaves members of the public at risk.
According to the charge details, Maxwell had a stash of explosives in purpose-built hides in England and Northern Ireland.
Last March, police said bomb-making parts had been found in barrels hidden in a wooded area in Carnfunnock County Park in County Antrim.
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Two months later, another “terrorist hide” was found in Capanagh Forest, also near Larne.
Police described it as one of the most significant arms finds in recent years.
Of particular concern to security chiefs was the discovery of military grade anti-personnel mines.
Pipe bombs and parts for making explosive devices made up part of the haul.
Their serial numbers revealed they had been taken from the Royal Marines base in Somerset where Maxwell was based.
Court papers revealed that 12 hides were discovered in total.