Diana Barnato Walker, who died on April 28 at 90, occupied an almost legendary position in the world of aviation: as well as being one of a handful of “Atagirls,” women who served during the war as Air Transport Auxiliary pilots delivering newly-built and battle-ready aircraft to airfields all over southern England, in 1963 she became the first woman in the world to break the sound barrier.

The diminutive socialite granddaughter of a South African diamond millionaire, before the war, Barnato Walker was well known in London for her high spirits and late nights spent at the Embassy or 400 Club in London. She was also known for the Bentley she was given for her 21st birthday — a gift from her doting father, motor-racing champion Woolf “Babe” Barnato.

In 1938, she decided to try her hand at flying and gained her license after only six hours of training. Three years later, she abandoned her affluent lifestyle to rough it in the ATA. By the age of 22 she had delivered 240 Spitfires and many other aircraft and narrowly survived several brushes with death.

It was said that the Atagirls tended to come in two models — cropped hair and sensible shoes, or “powder puff.” That Barnato Walker was one of the latter variety was clear from her autobiography, “Spreading My Wings,” in which she described an occasion when, delivering a Spitfire, she decided to try some aerobatics but got stuck upside down: “While I was wondering what to do next, from out of my top overall pocket fell my beautifully engraved silver powder compact. It wheeled round and round the bubble canopy like a drunken sailor on a wall of death, then sent all the face powder over everything.”

The ATA expected its pilots to fly in all weathers without navigational aids. As a result of this, and the fact that they flew unarmed and without radios, service in the ATA was one of the most dangerous activities available to either sex in the whole war. Out of the 108 female pilots recruited during the war, 16 were to perish in the air – including the first woman to fly solo from England to Australia, Amy Johnson, who died ferrying an Oxford aircraft in 1941.

Barnato Walker attributed her survival to her “guardian angel” and a man who had accosted her as she was about to take off on her first solo flight at Brooklands, whose hands and face were horribly burned. “He looked at me and said, ‘Don’t fly, Miss Barnato. Look what it’s done to me.’ After that I was a very careful pilot.”

Barnato Walker was born on January 15, 1918 into a gifted and enterprising Jewish family. Her grandfather, Barney Barnato, began as a trader and juggler in the Mile End Road, saved 50 pounds, and hitched his way to Johannesburg, South Africa, where he became co-founder of the De Beers mining group.

Her father, Woolf, inherited his father’s millions at 2-years-old, after Barney Barnato mysteriously fell or jumped over the side of a ship taking him to England in 1897. Woolf Barnato went on to win the Le Mans 24-hour car race for three consecutive years from 1928 to 1930, was also a “plus” handicap golfer, a first-class shot, a county-level tennis player, a top horseman, and a champion swimmer and skier. Barnato Walker and her sister, Virginia, were the daughters of Woolf Barnato’s American-born first wife. The marriage foundered when Barnato Walker was 4-years-old, and the two girls were brought up by their mother and an army of nannies and governesses in a large house on Primrose Hill.

After leaving Queen’s College in 1936, Barnato Walker came out as a debutante. But she quickly tired of being chaperoned and decided that the only way to escape the benign oversight of mother, nannies, and governesses was to learn to fly.

This ambition took her to Brooklands where, in 1938, she spent her pocket money on a few hours’ flying instruction in a Tiger Moth, going solo after six hours. At the outbreak of hostilities in September 1939, she volunteered as a Red Cross nurse but soon determined to apply for a job as a ferry pilot and was accepted into the ATA training program.

In 1942, Barnato Walker fell in love with a dashing Battle of Britain fighter ace, squadron leader Humphrey Gilbert.

Three weeks after meeting, they were engaged. Three days after that, circling over his base at Debden in a Tiger Moth, she was surprised that there was no sign of his blue-nosed Spitfire. After a series of frantic telephone calls, she was told that he had been killed the previous day.

In 1944 she married Derek Walker, another decorated pilot. They took an unauthorized honeymoon trip to Brussels, each piloting their own Spitfire, as a consequence of which Walker was docked three months’ pay.

Four months after the end of the war he too was killed, flying to a job interview in a Mustang. Unlike most of her fellow Atagirls, who found it impossible to forge a career in commercial aviation after the war, Barnato Walker obtained a commercial license and was appointed corps pilot for the Women’s Junior Air Corps.

One evening in 1963 in the mess at RAF Middleton St. George, the Wing Commander Flying, John Severgne, idly suggested that Barnato Walker might like to fly one of the RAF’s new supersonic Lightnings. She jumped at the chance and on August 26, 1963, following clearance from the Ministry of Defence, took off and reached a speed of Mach 1.65 (1,262 mph), making her the first woman to break the sound barrier.

Walker continued flying for a few more years with the WJAC. She also became MFH of the Old Surrey and Burstow Hounds, commodore of the ATA Association, and took up sheep farming in Surrey.

She was appointed MBE in 1965.

For 30-odd years she kept up a relationship with American-born racing driver Whitney Straight. They had a son, though Barnato Walker never asked Straight to leave his wife.

“I was perfectly content,” she explained. “I had my own identity.”