LONDON (AP) — Queen Elizabeth II has reached a major milestone by becoming the longest-reigning monarch in Britain's history, passing Queen Victoria, who served for 63 years and 7 months.

Prime Minister David Cameron said Wednesday that millions would celebrate the queen's "historic moment."

"Over the last 63 years, Her Majesty has been a rock of stability in a world of constant change and her selfless sense of service and duty has earned admiration not only in Britain, but right across the globe," Cameron said.

Buckingham Palace marked the event by releasing an official photograph of the queen taken by Mary McCartney, a photographer who is the daughter of former Beatle Paul McCartney.

Elizabeth came to the throne in 1952 upon the death of her father King George VI.