Enlisting as a private in the Gordon Highlanders, he was sent to an OCTU and then summoned to the War Office. There he met Andrew Croft and Peter Fleming, lifelong friends. After a hectic course in explosives they were dispatched to Finland, and disrupted the railways before the Finns capitulated.
Munthe arrived in southern Norway as liaison officer to the Norwegian army in March 1940, the same time as the Germans. After being wounded in the leg and captured, he was "allowed" to escape to Sweden by a friendly German army ex-medical student who was supposed to hand him over to the Gestapo.
Back in England, he was sent for by Sir Charles Hambro, the head of the Special Operations Executive. From August 1941 to the end of 1942 he ran the SOE's Norwegian section, before returning to the field, this time to "Massingham", the SOE base in North Africa.
In summer 1943 he travelled to Sicily and then to Salerno to contact Italian resisters. He went over to Capri to ensure that his father's villa, San Michele, was requisitioned for the English, set up a small unit on the island, and from it one of his best coups took place. Benedetto Croce, the brave anti-Fascist philosopher whom neither Hitler nor Mussolini had dared to silence, was living in the Villa Tritone at Sorrento. The Allies persuaded him to leave at dead of night with his elder daughter. Next morning the Germans surrounded the villa. Munthe decided to rescue Signora Croce and her daughter himself, and with Alberto Tarchiani (later Italian ambassador to Washington) set off for the villa. Luckily the guards had withdrawn to repair a bridge bombed by the RAF, and the rescue was swiftly effected.
Soon afterwards Munthe set up headquarters in liberated Naples. On 6 February 1944, he and Michael Gubbins (son of General Sir Colin Gubbins) were hit by a mortar shell while trying to get through the lines of Cassino. Gubbins was killed outright and Munthe so severely wounded that he took no further part in the war.
Malcolm Grane Munthe, soldier and preservationist: born London 30 January 1910; married 1945 Anna Rea (one son, one daughter, and one son deceased); died London 25 November 1995.