The two women share a passion for military history and a love of horses.
They are often spotted riding together at weekends in the magnificent grounds of Windsor Park.
The prince’s elder siblings all married at either St James’ or Westminster Abbey.
Their engagement was announced on 6 January 1999, and from the start the couple emphasised their desires for a low-key royal wedding devoid of ceremonial elements.
The Queen has been known to turn up unannounced at Edward and Sophie's Surrey home for afternoon tea.
In 2012, in celebration of the Queen's Diamond Jubilee, the Earl and Countess represented the monarchy on an official visit to Gibraltar, signalling the Queen's confidence in the couple.Speaking in a rare interview to mark the milestone, the earl gushed about his fond memories of his wedding day.He explained the day had been one of the best moments of his life adding it was "great fun and over far too quickly".Not even the prime minister was invited to the wedding.The dress code was also more relaxed, and as it was an early evening wedding, the guests were required to wear evening dress, not formal court dress.