In 60 years, the Queen has never put a foot wrong in public.
And for the last 24 of them, it turns out she's had a secret weapon - the unassuming Ella Slack.
The former BBC manager has, unbeknown to anyone except a handful of key advisers, spent the last quarter of a century acting as the Queen's official stand-in at rehearsals for royal events.
The 69-year-old from the Isle of Man has never accepted a penny for her loyal service, considering it 'a pleasure and an honour' to ensure that everything runs smoothly for the sovereign.
'How many people in the world have had a chance to sit in a royal landau or walk onto the dais at Windsor Castle even before the Queen has done so?' she said.
While Miss Slack may not resemble the Queen facially, she has a similar build to the monarch, standing just shy of 5ft.
The Queen is 5ft 2in.
She began her remarkable role in 1988, when she was working as manager of the BBC's sports and events department.
A producer asked her if she could stand in
for the Queen to check camera angles at a rehearsal for Remembrance Day at the Cenotaph - and her second career was born.
Since then, from the State Opening of Parliament to the 50th anniversary of VE day, wherever the Queen is on duty Miss Slack is likely to have been there first.
She has perfected her own version of the Queen's wardrobe, including a black patent handbag she bought in a charity shop for £1, and even styles her hair like the Queen.
Most recently, Miss Slack has been rehearsing for next weekend's Thames Diamond Jubilee Pageant, braving the wind and rain on the royal barge.
And she has won a coveted place in the flotilla on the day itself - in a boat named, appropriately enough, the Queen Elizabeth.
Source: Daily Mail