Back in 1953, a new "tradition" was invented to celebrate the coronation of Elizabeth II. A brand new recipe was released to mark the day; Coronation Chicken, which was cold chicken in cream sauce with sultanas. It's still sold in supermarkets to this day as sandwich filler. Practically everyone in Britain has eaten it at some point, and very tasty it is too.
As with any idea in Britain that is successful, it becomes a tradition - so a new recipe has been released to mark the coronation of King Charles III; Coronation Quiche. Here is the recipe:
Here is a video from the palace chefs showing how to make it:
Most people like spinach, and they like quiche, so this could be successful. If people are still buying a version of this in supermarkets in 10 years time, the tradition is set, and Prince William will release another coronation recipe when it's his turn to be crowned.