The lunch includes extended family members, which is the last time the Queen and Prince Philip will see them until they return from their Sandringham Estate at the beginning of February.
No doubt we will see the entire Cambridge clan: Prince William, wife Kate Middlteon and their three kids Prince George, Princess Charlotte and Prince Louis.
Meghan Markle and Prince Harry will be there as will Prince Andrew, Princess Beatrice, Prince Charles and Camilla, Prince Michael of Kent, the Duke of Gloucester and Lady Amelia Windsor.
The last time we saw this many royals was back at the weddings... And of course Trooping the Colour!