BALD and bespectacled, he seemed an unlikely commando, but a new book reveals how a Polar explorer from Glasgow led one of the most daring and important secret operations of the Second World War.

Alexander 'Sandy' Glen, a naval intelligence officer and Arctic expert born in 1912, was chosen to lead a party of exiled Norwegians to the strategically important island of Spitsbergen in the Arctic in 1942.

Fearing the Germans would use the Norwegian island as a base from which to mount attacks by bombers and warships on the Arctic convoys taking vital military aid to the Soviet Union, the Royal Navy devised Operation Fritham, a top secret mission to occupy Spitsbergen.

"Allied policy was to deprive the enemy of the use of Spitsbergen, provided this could be done by a small mobile force with minimal demand on the war effort elsewhere," Mr Glen later explained.

Having taken part in two expeditions to Spitsbergen in the 1930s and being one of the UK's leading authorities on the Arctic, Mr Glen was considered the ideal choice for the mission.

After carrying out an aerial reconnaissance of the island in an RAF Catalina flying boat based at Sullom Voe in the Shetlands, he took his 85-strong force on two small ships to Spitsbergen in early May.

But, unaware that the Germans had already established a small, secret base on the island, disaster struck when the Luftwaffe spotted the two ships in a fjord in Spitsbergen and bombed them with Focke-Wulf Condor aircraft, killing fifteen.

With most of their supplies and radio transmitter destroyed in the attack, Mr Glen and the survivors were stranded on the inhospitable island, 1000 miles from the nearest Allied territory.

Flight Lieutenant Ernest Schofield, navigator of the Catalina based at Sullom Voe that supported the Operation Fritham team, said: "The survivors needed help urgently, and the only way to provide it was by airlift."

For the next six weeks the men were resupplied by airdrops from the Catalina, flying extreme long-range sorties from the Shetlands to Spitsbergen, the furthest north any RAF aircraft had ever ventured.

On June 16, the flying boat was able to land in a fjord and take Mr Glen back to Scotland.

Determined to successfully complete the mission, just a few days after arriving back in the UK Mr Glen returned to the island by flying boat, while Norwegian reinforcements were landed soon after by Royal Navy vessels and destroyed the German base on Spitsbergen.

The island remained in Allied hands for the remainder of the war, providing an important refuelling stop for destroyers escorting supply convoys to Russia.

Mr Glen went on to serve with the Special Operations Executive in Yugoslavia and was awarded the Norwegian War Cross for his part in Operation Fritham. After the war he became chairman of the shipping and travel firm Clarksons and also a director of British European Airways.

Knighted in 1967, he died in 2004 at the age of 91.

l Arctic Airmen by Roy Conyers Nesbit is published by The History Press and is priced £20.