Calmness and modesty are qualities that sit well together when the slightest miscalculation can bring immediate disaster. John Bridge was a schoolmaster of pacifist inclination at the outbreak of the Second World War, but he volunteered his services when he saw that his physics degree could be put to work to save lives. Well before the fall of France and evacuation of the British Army via Dunkirk in June 1940, the Luftwaffe had been attacking England’s South Coast ports and, by accident or design, ten per cent of its bombs did not explode on impact.

Bridge was interviewed on June 4, commissioned into the Royal Naval Volunteer Reserve on the 13th, given one week’s familiarisation training on German bombs at RAF Manby, collected his uniform from Austin Reed, Piccadilly, on his way to Portsmouth on the 27th and defused his first unexploded bomb at Plymouth five days later.

In the ensuing five months, the three bomb-disposal teams under his command dealt with more than 100 “UXBs” in the Plymouth-Falmouth area. On December 27, the London Gazette announced the award of the George Medal to Bridge for his calm courage in making safe a bomb known to be fitted with a delayed action fuse, which could have exploded at any moment.

As the German Blitz on London and the South of England intensified during that winter, Bridge and his small teams of bomb-disposal experts were in constant demand. He dealt personally with 15 unexploded bombs during the raids on Plymouth on the nights of March 20 and 21, 1941.

One, a double-fused bomb designed to prevent handling, fell close to Devonport dockyard and was ticking ominously when Bridge reached it. He knew the magnetic field of his electric “clock-stopper” would automatically set off the Rheinmetall No 50 anti-handling fuse alongside the clockwork fuse. Calmly he neutralised the No 50 by liquid discharge, which took him an hour. Then he applied the clock-stopper to the main fuse.

This slowed but failed to stop the ticking, so he very gingerly unscrewed and withdrew the clockwork fuse. The bomb was blown up on Dartmoor and Bridge was awarded the King’s Commendation for Brave Conduct.

A few weeks later on May 17, a bomb fell into the sluice valve chamber between two docks at Falmouth and failed to explode, temporarily rendering both docks unusable. The bomb lay in six feet of water at the foot of the sluice chamber. Bridge climbed down the shaft cross-girders and, noting a hole in the bomb casing, unscrewed the base plug, slid a cable in and out through the casing hole and called for the bomb to be winched clear of the water. He held it away from the cross-girders until it was at a level for him to disarm it where it hung. In the shaft at 35 feet below ground level there was no possibility of escape had the bomb exploded. For this act of cold courage, Bridge received a Bar to his George Medal.

While the Luftwaffe threat gradually receded, that of unexploded sea mines in harbours and their approaches did not. Bridge was sent to the Simons Town naval base in South Africa, thought vulnerable to mines. At his own suggestion he was taught to dive using a Siebe Gorman helmet and pump apparatus. He was then posted to the Mediterranean theatre.

In August 1943, after the invasion of Sicily, he was instructed to clear Messina harbour of mines, as it was needed for vessels preparing the assault on the Italian mainland. A previous mine-clearing team had all been killed or seriously injured by depth charges left in the harbour waters. As the depth charges had an unknown firing mechanism, the first task Bridge faced was to recover one of them intact so that he could learn how to make the remainder safe.

It was necessary to suspend diving from time to time because of enemy shellfire. But, over a period of 20 hours and supported by his three-man team above water, Bridge made 28 dives in Messina harbour, cleared all the new type of depth charges and made safe a total of 207 other explosive devices above or below water. In consequence, Messina harbour was opened for use by ferries transporting troops of the Eighth Army across the straits to the toe of Italy on September 3, 1943.

Two of his crew who had handled the cleared charges above water received the George Medal. Bridge was awarded the George Cross for his “conspicuous and prolonged bravery and contempt of death in clearing Messina harbour”.

But his war was far from over. On D-Day+1 he went to Normandy to supervise the clearing of the beach at Arromanches of mines and a mass of other explosive devices left there. Then, at the end of September 1944, he was called forward to the Nijmegen area where a daring German operation was holding up the advance of General Sir Brian Horrocks’s 30 Corps over the River Waal. A group of German frogmen had floated specially designed charges downstream, placed them against the piers of the railway and road bridges, destroyed the former and damaged the road bridge. One of the charges had exploded, blowing a large hole in the road, but the other lay unexploded in shallow water against the pier.

Called during the night from Antwerp where he was working on harbour clearance, Bridge was flown in an ancient RAF Avro Anson up to 30 Corps headquarters along the air corridor at an altitude of 100 feet to avoid enemy air attack. He was greeted by General Horrocks with an offer of breakfast, but declined. Later that morning he stripped to his underpants to examine the cylindrical object lying below the surface of the Waal against the pier of the Nijmegen end of the road bridge.

As with the bomb in the Falmouth sluice chamber, he managed to secure a line to the bomb, have it winched above the water and into an assault boat. There he made it secure. On return to Antwerp, Bridge was met by his commanding officer with the words: “I thought of recommending you for another gong, but you’ve had your quota.”

He was the first person to be awarded a Bar to the George Medal. One other mine disposal hero — an Australian, Lieutenant Hugh Syme, RNVR — also received the GC, GM and Bar.

John Bridge was born at Culcheth, near Warrington, Lancashire, in 1915. He was the fourth of seven children of Joseph and Mary Bridge who farmed in the district. He attended Leigh Grammar School before going to King’s College London to read physics and science.

After taking degrees in both, he was appointed science master at Firth Park Secondary School in Sheffield, where he remained until he volunteered for the Royal Navy.

He returned to Firth Park after the war but was appointed assistant education officer for Southport in 1947. Subsequently he was director of education for Sunderland from 1963 to his retirement in 1976.

He married Jean Patterson in 1945. She died in August. Their three daughters survive him.

Lieutenant-Commander John Bridge, GC, GM and Bar, wartime bomb-disposal officer, was born on February 5, 1915. He died on December 14, 2006, aged 91