Belgium may have two kings from 21 July, they will not have the same title. Filip will be dubbed "King of the Belgians" and Albert "king", says Jan Van den Berghe. This is contrary to the Netherlands, where Queen Beatrix returned to being a princess after her abdication. In Belgium, however, the principle is: "Once king, always king."

After being sworn in, Filip will be called King Filip, and not Filip I. This extra "number" will only be introduced once there is a second king with the same name as Filip. For the moment, this does not seem very likely. The next in line to the throne will be Elisabeth, the eldest daughter of Filip and Mathilde, who turns 12 on 25 October. This is after legislation has been changed, as in the past only men were eligible to ascend the throne.