Queen set to become longest reigning British monarch
The Queen will soon make history when she becomes the longest reigning British monarch.
On September 9, she will pass the record set by her great-great-grandmother Queen Victoria who, Buckingham Palace has calculated, reigned for 23,226 days, 16 hours and 23 minutes.
At this time of year the Queen is taking her traditional summer break at her private Scottish home of Balmoral.
But on the day she passes Victoria's milestone, the monarch, joined by the Duke of Edinburgh, will open the new Scottish Borders Railway and take a steam train ride on the new £294m railway.
Historian Dr Kate Williams described the length of the Queen's reign as a great source of strength for the monarch.
"It's a very significant milestone. The Queen will become the longest reigning British monarch in history. She came to the throne when she was older than Victoria. Victoria was only 18," Dr Williams said.
"It shows that our female monarchs last the longest. The Queen's longevity is a great source of her strength and popularity. She has lived through World War Two and throughout the 20th century. Many people will not have known a different monarch."
Queen Victoria, who died in 1901, acceded to the throne on June 20, 1837, and became the figurehead of a vast empire amid great industrial, cultural and scientific changes to society.
But she mourned the early death of her consort Prince Albert in 1861 for the rest of her life.
Princess Elizabeth became Queen Elizabeth II when she was 25 on the death of her father King George VI on February 6, 1952. Like Victoria, she has acted as a figure of continuity as the country has modernised.
She has served, with Philip at her side, through the 20th century, the millennium and into the 21st century, witnessing new technological advances and a succession of British governments of different political persuasions.
In December 2007, she became the longest living British monarch, overtaking Victoria who died when she was 81, and in May 2011, she became the second-longest reigning monarch in British history, when she overtook George III.