The 30-year-old was held at an address in Somerset on Wednesday lunchtime (August 24) and the Metropolitan Police Service (MPS) said a house in South Devon and a wooded area were being searched. 

Officers are also carrying out further investigations in County Antrim, Northern Ireland. The man, who is believed to be from Northern Ireland, was detained on suspicion of being involved in the preparation of acts of terrorism under section 5 of the Terrorism Act. He was taken to a West Country police station. 

He was arrested by officers from the MPS` Counter Terrorism Command (SO15), supported by colleagues from Avon and Somerset Constabulary and Devon and Cornwall Police. 

His detention, which did not involve armed officers, is reportedly linked to two suspected dissident republican arsenals uncovered in forest parks in Northern Ireland earlier this year. 

Two separate hauls of weapons were discovered in Carnfunnock and Capanagh parks near Larne, County Antrim, within three months of each other. 

An armour-piercing improvised rocket and two anti-personnel mines were among the cache recovered at Capanagh in May. Several pipe bombs, magazines and ammunition for an assault rifle as well as bomb component parts and command wires were also concealed in barrels in purpose-built holes in woodland. 

In March, bomb-making items were found at nearby Carnfunnock Country Park. Officers said four barrels were unearthed at Carnfunnock – two barrels were empty but two contained a variety of bomb-making components, including wiring, toggle switches, circuit boards, partially constructed timer power units, ball bearings and a small quantity of explosives. 

Today’s arrest was pre-planned and intelligence-led as part of an investigation into Northern Ireland-related terrorism being coordinated by SO15 in collaboration with Police Service of Northern Ireland (PSNI) and the South West Counter Terrorism Intelligence Unit. 

A statement from the MPS asked the public to “remain vigilant” in response to the threat from terrorism. 

It said: “The public can be reassured that there is no intelligence to suggest an immediate threat to our communities. 

“The man, who is a serving member of the British armed forces, was arrested at an address in Somerset and has been taken to a West Country police station.” 

The threat to Great Britain (England, Wales and Scotland) from Northern Ireland-related terrorism is classed as ‘substantial’ while the threat to Northern Ireland from Northern Ireland-related terrorism is ‘severe’.