Lieutenant-Colonel Richard Van Der Horst, commander of the Special Boat Service, the Royal Marines’ counterpart of the SAS, was the leading planner for a lightning raid that rescued six British soldiers from rebel fighters in Sierra Leone in 2000.

As Van Der Horst’s wife and two young daughters prepare for what is expected to be a quiet family funeral this week, senior officers have given details both of his high-flying career and of the incident on a mini-submarine in a Norwegian fjord that led to his death.

Van Der Horst, from London and in his early forties, was himself the son of a former SBS chief and won the sword of honour on passing out as the best junior officer in 1988.

A senior army colleague said: “He was an outstanding man, an enormously popular and outward guy who I would have no doubt was destined to be at least director of special forces, a position never held by someone from the SBS.”

Van Der Horst, said the officer, was highly regarded by both the SBS and the SAS, adding: “And there is not a lot of love lost between them.”

Another source added: “As commanding officer he didn’t have to do these exercises, but he did not want to lose touch with his men. He liked to keep his hand in at the sharp end and that bravery cost him his life.”

When he became trapped in the sub, Van Der Horst was taking part in Nato’s exercise Battle Griffin. He was with a group of SBS frogmen near the Olavsvern naval base, deep inside the Arctic Circle near Tromso. Some of the 14,000 personnel on the exercise were training in how to retake oil rigs and ships from Al-Qaeda terrorists.

In the minutes leading up to the incident, Van Der Horst was on board a six-seat Mark 8 Swimmer Delivery Vehicle (SDV). The mini submarine was designed for the US Navy Seals special forces and can carry frogmen undetected over 50 miles underwater. It has a pilot and navigator at the front, with four other men and equipment in a compartment behind. All on board must carry full diving gear, including oxygen, as the SDV has no air of its own.

A special forces source said Van Der Horst was in the back of the SDV. It seems he encountered difficulties with his oxygen supply and could not get out of the submersible.

The rest of the team were already out and swimming freely, said the source. They struggled to free Van Der Horst over the next 10 minutes as he gradually ran out of oxygen.

It is believed Van Der Horst was unconscious when he was brought to the surface. He spent a week on life support in hospital but never came round. His wife was at his bedside when he died last Monday.

The Ministry of Defence has disclosed little of the incident, in line with the practice of not reporting special forces’ work. The ministry is also awaiting the outcome of an inquiry.

Fellow soldiers, however, paid tribute to a man who seems to have been distinguished even by special forces standards.

Unlike most of the forces, which are being cut sharply, the SBS has grown — from 100 combat troops five years ago to a total combat strength of some 250 in three squadrons now, more than half the size of the SAS.

Van Der Horst spent part of his early career specialising in mortars and later fought in the first Gulf war in 1991.

In Sierra Leone he helped plan the mission in which SBS frogmen moved along a creek, joining SAS and Parachute Regiment soldiers who burst out of the jungle. They routed the West Side Boyz militia, freeing the British soldiers. One SAS man was killed in the attack.

Van Der Horst won an OBE for services in the second Gulf war in 2003, when the SBS helped prevent Saddam Hussein’s forces blowing up oil installations in southern Iraq.

When he became commander of the SBS, Van Der Horst was emulating his father Rupert, now a brigadier, who led the service from 1978 to 1980. Last week tributes to Van Der Horst were posted on a marines’ internet message board. One read: “Knew this man as a young troop officer . . . excellent officer who led by example.”

Additional reporting: Jonathan Tisdall

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