Secret weapon behind the Spitfire – a 13-year-old north London schoolgirl

The secret story of a schoolgirl who helped engineer the new generation of Spitfire and Hurricane fighter planes, that were deemed crucial in winning the Second World War, has been revealed for the first time to mark the Battle of Britain’s 80th anniversary.

In the summer of 1934 Hazel Hill, a 13-year-old girl from north London, was approached by her father, Captain Fred Hill, a scientific officer in the Air Ministry who was trying to make the case for the new generation of fighter planes.

Despite her youth, Captain Hill drew upon his daughter’s mathematical intellect and discussed plans with her as to how it could be possible to arm Spitfires with eight machine guns, as opposed to the four which had been originally suggested.

The number was seen as “radical” by Captain Hill’s superiors, who were concerned that the sheer weight of the guns would weigh down the planes, and it would be impossible to fit them.

With a calculating machine and the latest gun firing analysis, Captain Hill and his teenage daughter sat at the kitchen table and mocked up calculations of how to make it work.

Together, they devised how it would be possible to arm what would become the Spitfire and Hurricane with double the amount of Browning .303 machine-guns.

They calculated the exact distance the fighters had to be from the enemy aircraft to successfully hit their target and bring it down in two seconds - the amount of time a pilot could be expected to keep an enemy in their sights - it would have to have eight machine guns that could fire one thousand rounds a minute.

Following a crucial meeting of armament specialists at the Air Ministry in July of that year, Captain Hill  presented a graph showing the results of their calculations, with only himself and his superior officer aware of his daughter’s involvement in the calculations.

The plane specifications for the new Spitfire and Hurricanes were subsequently changed to being armed with eight guns.  In the book "I Hold my Aim" by Group Captain Claude Hilton Keith, a British-Canadian aviator who fought with the RAF in the Second World War, he wrote that “the deliberations of that conference made possible, if not certain, of the winning of the Battle of Britain, almost exactly six years later”.

The Battle of Britain, which was fought 80 years ago, from July 10th until October 31, 1940, saw 3,000 fighter pilots save Britain from Nazi invasion when they defended the skies against the Luftwaffe.

More than 500 RAF pilots and aircrew were killed in the aerial battle, which led Churchill to declare "Never was so much owed by so many to so few" in a speech on August 20, 1940.

Group Captain James Beldon, of the Royal Air Force, said Hazel's important contribution as a teenager was “vital to this country’s survival”.

“Eight was seen as radical,” he said in the BBC documentary "The Schoolgirl Who Helped to Win a War".

“In air combat the margins are very, very fine and it’s quite reasonable to think that the outcome could have been quite different.”

Hazel’s reward was permission to sit briefly in the cockpit of the plane she had helped design.

She went on to have a career in medicine with the NHS, where she worked for 44 years and with her husband, Chris, raised four sons.

One of her children, Frank, said: “If you are a 13-year-old girl at your kitchen table, you can change the world.”

Another of her sons, Ted, added that history “should remember her as being one of the people who made a real difference”.

“The eight guns were only just enough to win the battle,” he added.  “It’s amazing history hangs on so fine a thread. If she had got the calculations wrong, or if she hadn’t been asked to help, if the decision had not been made to go with eight guns, who knows what would have happened.”

The story has been a family secret for years and emerged when her granddaughter, Felicity Baker, a BBC journalist, dedicated 18 months to pulling the pieces together.

You can watch Hazel’s story on The Schoolgirl Who Helped To Win A War on the BBC News Channel on Saturday 11th July at 1:30pm, 5:30pm and 8:30pm or on Sunday 12th July at 10:30am and 4:30pm.