His exploits - charging up beaches dressed only in a kilt and brandishing a dirk, killing with a bow and arrow, playing the bagpipes at moments of extreme peril - and his legendary escapes won him the admiration and devotion of those under his command, who nicknamed him "Mad Jack".
Churchill believed an assault leader should have a reputation which would at once demoralise the enemy and convince his own men that nothing was impossible. He was awarded two DSOs and an MC, and mentioned in despatches.
Romantic and sensitive, he was an avid reader of history and poetry, knowledgeable about castles and trees, and compassionate to animals, even to insects.
John Malcolm Thorpe Fleming Churchill was born in Surrey on Sept 16 1906. His father, Alex Churchill, was on leave from the Far East, where he was Director of Public Works in Hong Kong and Ceylon.
After education at the Dragon School, Oxford, King William's College, Isle of Man, and Sandhurst, Churchill was commissioned in 1926 into the Manchester Regiment and gazetted to the 2nd Battalion, which he joined in Rangoon.
Returning from a signals course at Poona, he rode a Zenith motor-cycle 1,500 miles across India, at one point crashing into a water buffalo. In Burma, he took the Zenith over railway bridges by stepping on the sleepers (there was nothing in between them) and pushing the bike along the rails.
Churchill moved from Rangoon to Maymyo where he was engaged in "flag marches", which meant moving up and down the Irrawaddy by boat, visiting the villages and deterring those who might be contemplating robbery, murder or dacoity.
At Maymyo he learned to play the bagpipes, tutored by the Pipe Major of the Cameron Highlanders, and became an oustanding performer. But when the regiment returned to Britain in 1936, he became bored with military life at the depot at Ashton-under-Lyne and retired after only 10 years in the Army.
Churchill went on a grand tour of Europe, accompanied by his great friend Rex King-Clark; took minor parts as an archer in films; played the bagpipes as an entertainer; and represented Great Britain at archery in the 1939 World Championships.
On the outbreak of war in 1939, he was recalled to the Colours and went to France, taking with him his bow and arrows which he used on patrols against the Germans in front of the Maginot Line. The weapon was silent, accurate to 200 yards and lethal.
After the Germans attacked in France, Churchill was awarded the MC in the retreat at the Battle of l'Epinette (near Bethune) where his company was trapped by German forces.
Churchill fought back with two machine guns (and his bow) until ammunition was exhausted, then extricated the remains of the company through the German lines at night and reported back to Brigade HQ. Later he was wounded and carried a bullet in his shoulder all his life.
After returning to England, he joined the Commandos and in 1941 was second-in-command of a mixed force from 2 and 3 Commandos which raided Vaagso, in Norway. The aim was to blow up local fish oil factories, sink shipping, gather intelligence, eliminate the garrison and bring home volunteers for the Free Norwegian Forces.
Before landing, Churchill decided to look the part. He wore silver buttons he had acquired in France; carried his bow and arrows and armed himself with a broad-hilted claymore; and led the landing force ashore with his bagpipes. Although he was again wounded, the operation forced the Germans to concentrate large forces in the area.
After recovering, Churchill was appointed Lieutenant-Colonel commanding No 2 Commando which he took through Sicily (leading with his bagpipes to Messina) and then to the landings at Salerno.
They captured the village of Pigoletti and its garrison of 42 men as well as an 81 mm mortar and its crew. In further fighting along the Pigoletti Ridge, he was recommended for the VC but eventually received the DSO. His action had saved the Salerno beachhead at a critical time.
Churchill's next assignment was in the Adriatic, where he was appointed to command a force comprising No 43 Royal Marine Commando plus one company from the Highland Light Infantry and eight 25 lb guns.
They landed on the island of Brac, then attacked and captured the Vidova Gora (2,500 ft high), the approaches of which were heavily mined. Playing his pipes, Churchill led No 40 Commando in a night attack which reached the top of the objective where he was wounded and captured.
"You have treated us well," he wrote to the German commander after only 48 hours in captivity. "If, after the war, you are ever in England and Scotland, come and have dinner with my wife and myself"; he added his telephone number. The German was one Captain Hans Thornerr and later that note saved Thornerr's life when the Yugoslavs wanted to have him shot as a war criminal.
The Germans thought, wrongly, that Churchill must be a relation of the Prime Minister. Eventually he was imprisoned in Sachsenhausen Camp, near Berlin, where he was chained to the floor for the first month and found himself in company with such VIPs as Kurt von Schusnigg, the former Chancellor of Austria, von Thyssen, and Schacht, the former German Economics Minister.
Churchill tunnelled out of the camp with an RAF officer, but was recaptured and transferred to a PoW camp in Austria. When the floodlights failed one night he escaped and, living on stolen vegetables, walked across the Alps near the Brenner Pass. He then made contact with an American reconnaissance column in the Po Valley.
Churchill was appointed second-in-command of No 3 Commando Brigade, which was in India preparing for the invasion of Japan, but the war ended - much to his regret, as he wanted to be killed in battle and buried in the Union flag.
He took a parachute course, making his first jump on his 40th birthday, and commanded 5th (Scottish) Parachute Battalion, thus becoming the only officer to command both a Commando and a Parachute battalion.
Churchill had always wanted to serve with a Scottish regiment, and so transferred to the Seaforth Highlanders, becoming a company commander.
In 1948 he was appointed second-in-command of the Highland Light Infantry, then serving in Jerusalem. Terrorism was widespread and on April 13 1948, Arabs ambushed a Jewish convoy of doctors en route for the Hadassah Hospital, near Jerusalem.
Churchill, having ordered reinforcements for his small force, walked alone towards the ambush, smiling and carrying a blackthorn stick. "People are less likely to shoot you if you smile at them," he said. So it proved.
He then managed to evacuate some of the Jews but they thought that Haganah (the Jewish army) would save them and did not require his services. As one of the HLI had now been killed by Arab fire, he withdrew; 77 Jews were then slaughtered. Later Churchill assisted in the evacuation of 500 patients and staff from the hospital.
Back in Britain, he was for two years second-in-command of the Army Apprentices School at Chepstow before serving a two-year stint as Chief Instructor, Land/Air Warfare School in Australia.
In 1954, Churchill joined the War Office Selection Board at Barton Stacey. During this period he rode a surf board a mile and a half up river on the Severn bore.
His last post was as First Commandant of the Outward Bound School.
After retirement, Churchill devoted himself to his hobby of buying and refurbishing steamboats on the Thames; he acquired 11, which made journeys from Richmond to Oxford. He was also a keen maker of radio-controlled model boats, which he sold at a profit. He also took part in motor-cycling speed trials.
When not engaged in military operations Jack Churchill was a quiet, unassuming man, though not above astonishing strangers for the fun of it. In his last job he would sometimes stand up on a train journey from London to his home, open the window and hurl out his briefcase, then calmly resume his seat. Fellow passengers looked on aghast, unaware that he had flung the briefcase into his own back garden.
Jack Churchill married, in 1941, Rosamund Denny; they had two sons.
