Elizabeth II ascended/came to the throne (= became queen of Britain) when her father died.
伊麗莎白二世在她父親逝世後登上王位。
Queen Victoria was on the throne (= was queen) at that time.
那時維多利亞女王在位。
Charles is next in line to the throne (= will become king next).
查理斯將繼承王位。