Following his retirement from public life in 2017, the Duke made Wood Farm on the Sandringham Estate his main home.
However, during the pandemic, he has been reunited with the Queen and the couple have spent most of their time isolating together at Windsor Castle since last March.
While the Duke is understood to remain in good health, in the event of his death the Royal Family have a special codename under which they will enact his funeral plans.
Every senior member of the monarchy, including Prince Charles and the Queen, have code names which will be used in the immediate aftermath of their deaths.
