Elizabeth II longest-reigning British monarch

Elizabeth II overtook her great-great-grandmother Queen Victoria on Wednesday to reign longer than any other British monarch. Victoria died on January 22, 1901 after reigning for 63 years and 216 days.

Prime Minister David Cameron took the opportunity to celebrate the Queen's "historic moment," inviting millions of Britons to join him.

"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.

"It is only right that today we should celebrate her extraordinary record, as well as the grace and dignity with which she serves our country," he added.

Elizabeth was not participating in any official celebrations to mark the occasion, as the 89-year-old has cut back on international travel in recent years and lightened her workload. She attended several events to mark her Diamond Jubilee in 2012.

Buckingham Palace did however release a new official photograph in honor of the achievement:

Elizabeth II was never expected to take the throne, but did so because her uncle Edward VIII abdicated. She became Queen in 1952 at the age of 25, upon the death of her father King George VI.

Her official coronation took place a year later, watched by millions as one of the first major events broadcast on live television in Britain.

Elizabeth had already passed a little-noted milestone on June 23, when she surpassed 2 billion seconds on the throne. Should she still be reigning on July 18, 2020, she will have been monarch for 25,000 days.

sgb/es/jr (AP, dpa)