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.

The Duke and Duchess of Edinburgh once had to sleep in an unexpected location when staying at Sandringham House in Norfolk.

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