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The Queen will on Saturday become the oldest monarch Britain has ever had, in an event that will pass into history without fanfare or public celebration.
Her great great grandmother, Queen Victoria, was 81 years, seven months, four weeks and one day when she died in January 1901
after a reign of almost 64 years.
Queen Elizabeth II, who will spend the day quietly at Windsor Castle with the Duke of Edinburgh, will have outlived Victoria by one day this Saturday.
Her latest milestone comes just a month after she became the first monarch to celebrate a diamond wedding anniversary. Five years ago, she also became the oldest monarch to mark a golden jubilee.
However, she still has another eight years to go before she overtakes Queen Victoria as Britain's longest serving monarch.
The Queen, who turns 82 on April 21, is Britain's fourth longest reigning monarch, behind Henry III, who reigned for 56 years between 1216 and 1272, and George III, who had 59 years on the throne (1760 to 1820) and Victoria.
But while many octogenarians opt for a quiet life, the Queen, who celebrated the birth of her eighth grandchild this week, is showing no signs of slowing down. She is in good health and still undertakes more than 400 official engagements each year, including a state visit to Uganda last month.
Author and journalist Robert Hardman said the Queen's stamina and longevity was down to far more than modern medicine and genes.
"At an age when all of her contemporaries have long since retired, she has, very quietly, been something of a royal rebel," he wrote in the Spectator magazine this month.
"You might imagine that an institution governed by a woman of 81 (and with a husband of 86) would either be slowing down or handing on.
"The monarchy is doing neither. The Prince of Wales continues to support the Queen when required and he knows the ropes better than anyone (next year, he sets a record of his own when he overtakes Edward VII to become the longest-serving heir apparent in history).
"But this reign shows no signs whatsoever of the gentle withdrawal and stagnation one might have expected after 55 years."
And the Queen's cousin Margaret Rhodes believes she will never abdic-ate.
"When she took her coronation vow all those years ago, she promised to serve her country whether her life be long or short," Ms Rhodes told the Daily Mail.
"It is not a responsibility she will ever - if at all - give up lightly. I am sure that she will never abdicate."
- AAP