Story behind the photo: the Fab Four's tense royal reunion

It was Harry, Meghan, William and Kate's final official engagement together

Next week marks an important date in the British royal family's calendar: Commonwealth Day.

It's just been announced that on Monday 11 March, Queen Camilla and Prince William will lead members of The Firm in attending the traditional Commonwealth Day service at Westminster Abbey. They'll be accompanied by the Duke and Duchess of Edinburgh, the Princess Royal, the Duke and Duchess of Gloucester, and the Duke of Kent.

But notably absent in King Charles' slimmed-down monarchy will be the King himself, and Princess Kate, who are both out of action due to poor health.

The upcoming event is usually a big moment for the royals. It's a chance for some members of the family to reunite in public – we haven't seen them all together since Christmas Day – and for them to don their finest hats and glad rags. But it's also a time to celebrate the Commonwealth network of 56 countries, of which Charles is head of. It's a colourful, inclusive occasion that generates worldwide coverage.

Ahead of Monday's service, I’ve been thinking about the featured photo from the Commonwealth Day service of March 2020, which was taken during another period of difficulty for the royal family. Us royal fans tend to have pretty long memories but, in case some of the details of that turbulent time have faded, don't worry, in this post I will tell its tale…