The Queen will be joined by Charles and Camilla, William and Catherine and Harry and Meghan for the annual service at Westminster Abbey.
Royal commentator Richard Fitzwilliams tells us why this trip is so significant for the Duke and Duchess.
The 36-year-old joined Prince Harry at the Commonwealth Youth Forum earlier today.
The 33-year-old also had an awkward run-in with Theresa May.
The 36-year-old joins the royal family at the annual Commonwealth Day service.