The Queen has become the second-longest reigning monarch in 1,000 years of British history, overtaking George III.

George III reigned for 59 years, 96 days, plus 13 extra leap-year days, a total of 21,644 days. Only one royal ancestor has had greater longevity on the throne: the Queen's great-great-grandmother, Queen Victoria.

Queen Elizabeth, who celebrates her diamond jubilee next year, acceded to the throne on 6 February 1952 and has reigned for 59 years and 95 days, plus 15 extra leap-year days, a total of 21,645 days.

George III (1760-1820), dubbed "Farmer George" for his love of agriculture, was known for his "madness", which has since been diagnosed as porphyria. During his reign, Britain lost its US colonies. He had 15 children with his wife, Queen Charlotte.

Victoria, who was 18, when she became Queen, spent more than 63 years on the throne. Elizabeth will surpass Victoria's record in September 2015.

The record can be calculated in a number of ways. Variations take into account timings of George III's accession and death.