Ingrid said that just a year after they met, the Prince, who is the youngest son of Queen Elizabeth II and Prince Philip, got cold feet.
“Edward became what one friend described as ‘unnerved’ by the speed which the affair was developing.
“But if Edward was wracked by indecision (a not-uncommon problem amongst male members of his family) Sophie remained coolly determined.
“She was not prepared to let the relationship flounder.
“When rumours of the rift became public she dismissed them as ‘rubbish’.
“She was being elastic with the truth, but it did give her the breathing space she needed to get her relationship back on track again,” she wrote.
Everything was back on track by the Christmas of 1994, and the couple went on to wed at St George’s Chapel in June 1999.
They now have two children, Lady Louise Windsor, 15, and James, Viscount Severn, 11, who is the youngest grandchild of Queen Elizabeth.