Royal Marines have been testing their skills in challenging terrain and conditions across the Atlantic alongside their American counterparts.

Members of 40 Commando flew to California for Exercise Black Horse, a regular event which normally takes place on the East Coast.

Working out of the US Marine Corps base at Twentynine Palms, the ‘Sunshine Commando’ has been undertaking a combination of range work and a mountain training package in hot conditions in the Mojave Desert.

A Royal Marines spokesman said the switch to the West Coast had proved useful as the Royals did not often have the chance to train with American marines from that side of the country.

The base at Twentynine Palms is the largest such facility in the world, covering more than 900 square miles near the Joshua Tree National Park.

The Americans regard their so-called combat centre as the best in the world – and the fact that it attracts troops from around the globe to take part in live-firing exercises is powerful proof.

The area consists of steep mountains rising to around 1,500 metres with flat valleys, and the area is peppered with sand dunes and dry lakes.

Meanwhile, back over on the East Coast in Virginia, men of the Fleet Protection Group RM (FPGRM) have been involved in Exercise Tartan Eagle.

Around 50 troops from O Squadron flew on an RAF VC10 from Prestwick in Scotland to Norfolk Naval Base, where they were hosted by their American equivalents, the Fleet Anti-terrorist Security Team (FAST).

FAST are part of the Marine Corps Security Force Battalion, and their job roughly equates to that of the FPGRM, whose primary role is that of guarding Britain’s independent nuclear deterrent – they are based at Faslane on the Clyde.

Two five-day packages took them to Fort Pickett, some three hours inland from Washington DC, and up to the North West camp in the Chesapeake area.

The British troops were introduced to American weapons such as shotguns, Colt carbines and Beretta pistols in “challenging” conditions..

American platoon commander Capt Patrick Rapicault said: “The exercise provides an ideal opportunity to swap tactics and learn from each other’s experience and knowledge in urban patrolling and combat, and also that the camaraderie and shared pride in being Marines is clear to see.”

Close Quarter Battle training followed, which meant both sets of Marines developed their skills at three-man room clearance drills.

American drill instructor Sgt Jeremy Soles said: “The Royal Marines showed good aggression and were very keen to learn and a delight to train.”

Capt Jez Stemp RM said: “The US marines were very proficient at room-clearing drills and marksmanship, and this should rub off on the Squadron when carrying out their duties in the UK.”

Training also included practising Operations in Built-Up Areas, snap and instinctive shooting, and fast-roping drills.

The training culminated in a confirmatory exercise using blank ‘simmunition’ rounds and a US Marine Corps CH46 Seaknight troop-carrying helicopter.

There was also time for some rest and recreation in Washington and Virginia Beach.

Maj Shaun Webber, the Officer Commanding O Squadron, said that Tartan Eagle, the only existing bilateral training programme of its kind, had much to offer both sides.

“Our Marines compare very favourably with our American counterparts, but having said that we have learned a lot from the US Marines, particularly operating in a Close Quarter Battle environment.”