Personnel from the 43 Commando Fleet Protection Group Royal Marines, who guard the UK’s naval nuclear weapons, have honed their combat skills in Gibraltar.

The two-week intensive training is intended to maintain the readiness of the marines to protect the nuclear deterrent.

The 550-strong 43 Commando unit, which is based at HM Naval Base Clyde in Scotland, is the last line of defence tasked with safeguarding the Trident missiles and their deployment submarines.

Squadrons O and P trained in close-quarters battle skills and practised securing critical infrastructure. Gibraltar presented the marines with a challenging and unfamiliar environment.

Training resembled conditions at the Clyde base and included jetties in an industrial and maritime setting.

During the Serpent Rock 19 training exercise, the marines moved at night through underground tunnels, before taking up their first objectives around the jetties.

The marines faced enemy forces and completed their task before daylight broke. The 43 members also participated in a scenario that involved securing a mock village.

P Squadron commanding officer major Dan Sawyers said: “Gibraltar is one of a number of overseas training areas that 43 Commando uses to keep its marines at a high level of readiness for its role back in Scotland.

“Making use of Gibraltar’s training facilities, in particular its working dockyard and tunnel system, which require marines to adopt a whole variety of traditional and novel approaches, allows us to put our personnel under considerable psychological and physical stress in an unfamiliar environment.

“In the maritime-industrial environment, where in the space of just a 100m you can encounter a constantly changing landscape, marines were continuously forced to identify and quickly change their tactics to deal with any threats they face.”

In August this year, the marines of O and P Squadrons trained in the Netherlands.