In the UK, the public will be asked to pledge their own allegiance to the new King - out loud - when he's crowned next weekend.
It'll be the first time ever those watching or listening will be asked to join in.
In another first, representatives from different faith groups will also feature in the service.
Ruth Gledhill is a former religious affairs correspondent:
"The coronation service has elements of tradition in it that date back to the 10th century and before, and it's really beautiful and profound in that respect. But also it is very much rooted in the present, and in the reality of modern Britain, the diversity of Britain".
