Prince Edward and Duchess Sophie had a traditional royal wedding in 1999, but the early days of their romance were decidedly less formal. Queen Elizabeth II's youngest son first met Sophie in 1987 when she was working as a press officer at Capital Radio.

The Duke of Edinburgh title had previously been held by the King and Prince Edward’s father Prince Philip for more than 70 years. While Prince Edward and Duchess Sophie are senior working royals, their two children Louise and James are unlikely to do the same, and currently do not use HRH titles.

Specifically, William hopes to tap Prince Edward and Duchess Sophie's two kids, Lady Louise Windsor, 21, and James, Earl of Wessex, 17.

Much like Princess Kate, Duchess Sophie was a normal citizen prior to marrying into the Royal Family. In fact, Sophie, the Duchess of Edinburgh, had a successful career before she married Prince Edward. As a result, Sophie had to "reduce her expectations" in many respects after marriage.

The Duke of Edinburgh is currently on a visit to Estonia - just days before his wife's major milestone on Monday.

With so many stylish royals in the world, it’s hard to believe there’s even more regal fashion for Us to obsess over. But alas, there is one British dignitary whose wardrobe we just cannot get enough of these days: Sophie,