How Princess Diana’s cigarette-loving big sister – who dated Prince Charles – found love with a farmer instead of the heir to the throne

As Lady Sarah McCorquodale celebrates 44 years of marriage today, onlookers may wonder if she is reflecting on how different her life could have been.

Because Princess Diana’s eldest sister once dated Prince Charles, she went out with the heir to the throne two years before her sister.

In fact, Lady Sarah, 69, even introduced Diana to Charles and says she played ‘cupid’ for the pair.

But it was 22-year-old Lady Sarah Spencer, a willowy red-head with a great sense of fun, who first caught Prince Charles’s eye at a house party at Windsor Castle for Royal Ascot.

‘Prince Charles enjoyed Sarah’s sparkiness and irreverent wit and they made each other laugh,’ says Sarah Bradford, author of Diana: Finally, the Complete Story.

Their romance involved polo matches and an invitation to Balmoral but it was after a skiing trip to Klosters in 1978, that Sarah made the mistake that would end their liaison.