Elizabeth II's sister had to choose between cancelling her engagement and renouncing her title in 1955. Or did she? In 1978, the BBC talked to the war hero who almost married a princess.

When Princess Margaret announced on 31 October 1955 that she was ending her engagement to Group Captain Peter Townsend, it brought an end to a will-they-won't-they saga that had enthralled the nation. The enduring myth is of a trapped monarch, an uncompromising government and a 25-year-old woman forced to give up her dream wedding to a war hero. The princess, it seemed, was presented with a stark choice: she could either keep her royal privileges or live in quiet exile as plain old Mrs Townsend.

"I believe her decision was absolutely right in the circumstances," said Townsend on the BBC's Nationwide while promoting his autobiography in 1978, coincidentally on Valentine's Day. But confidential government papers released after Princess Margaret's death revealed that her options may not have been quite as drastic as they are sometimes portrayed.

Townsend was a genuine war hero who was highly decorated for his role in the Battle of Britain. Born in 1914, he had joined the Royal Air Force at the age of 19. Among his exploits as an ace fighter pilot, he helped to shoot down the first German bomber on English soil. Townsend told the BBC in 1995 how he had visited the plane's wounded rear gunner in hospital the following day: "I thought, this may happen to any of us, so I went to see him just to say, 'Well, we're not really enemies after all; we're human beings.'" Indeed, Townsend was himself later shot down but was largely unscathed, physically at least. As the air campaign ground on relentlessly, he recalled: "We became hardened killers who had no thought but for destroying the enemy."

By the end of the war, with his nerves shot, Townsend landed on his feet with a job in the Royal Household as King George VI's equerry: a trusted military officer charged with the smooth functioning of royal engagements and ceremonial duties. He was close to the family, living in the grounds of Windsor Castle and often accompanying the princesses on public engagements. The teenage Margaret really took notice of the dashing Townsend in 1947 on a tour to South Africa. Margaret was 17; Townsend was almost twice her age and married with two children.

If their friendship was deepening over time, it was all strictly hush-hush. In 2005, Margaret's friend Lady Jane Rayne recalled to the BBC's Timewatch that she witnessed the pair's chemistry at a shooting party in Balmoral in 1951, as the princess approached her 21st birthday. "Like the proverbial gooseberry, I felt I shouldn't have been there. They never kissed or held hands or anything, but you could just feel it," she said.

The princess had grown up to become a dazzling socialite, with stories of her party-going thrilling the world's press. But in February 1952, tragedy struck when her beloved father, King George VI, died aged just 56. Margaret's sensible older sister Elizabeth was next in the line of succession. At the late Queen's coronation in June 1953, a tabloid newspaper reporter spotted the princess flicking a piece of fluff off Townsend's jacket. While hardly something out of Bridgerton, this intimate gesture was enough to set tongues wagging.

In fact, Townsend had already proposed to her, a few weeks after his divorce. Elizabeth asked Margaret to wait for a year to let things settle down after the coronation. Under the Royal........

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