Queen Elizabeth II becomes Britain's longest-reigning monarch on 9th September 2015. She takes the record held by her great-great-grandmother Queen Victoria at around 5.30 pm on that day, having spent 23,226 days, 16 hours and 30 minutes on the throne. The exact moment is not known because her father, King George VI, died in his sleep at some point on 6th February 1952. The Queen, who was born on 21st April 1926 in London, received the news while on a royal tour in Kenya. She acceded to the throne at the age of 25. Her coronation took place just over a year later on 2nd June 1953. A total of 12 prime ministers so far, from Winston Churchill to David Cameron, have held office during her reign.

Queen Victoria reigned for 63 years and seven months (precisely 23,226 days, 16 hours and 23 minutes) between 1837 and 1901. She became queen at the age of 18 after her uncle William IV died. During her reign, Britain's empire reached its height. The country experienced a massive expansion of its industry and wealth. Queen Elizabeth’s reign has seen Britain’s recovery in the years following World War II, the dismantling of its empire and its becoming a member of the European Union. Victoria set her own record as longest-serving monarch on 23rd September 1896 when she overtook her grandfather George III (1760–1820), Britain’s longest-reigning king.

Elizabeth’s record-breaking reign means there are now three generations of future monarchs alive today. Her eldest son Prince Charles, aged 66, is the longest-serving heir to the throne in British history, having been so since the age of three. The Queen’s husband, the 94-year-old Duke of Edinburgh, is the longest-serving consort to a British monarch in history.

Besides the UK, Elizabeth is queen of 15 other nations, including Australia, Canada, Jamaica and New Zealand. Following the death of 90-year-old King Abdullah of Saudi Arabia in January 2015, Queen Elizabeth II, now 89, became the oldest monarch in the world. She is only the second longest-serving, however. The 87-year-old King Bhumibol Adulyadej of Thailand acceded to the throne in 1946.