The Queen will break the record of her great-great-grandmother, Queen Victoria, on Wednesday, serving more than 63 years and 216 days on the throne.
The new portrait released to mark the day is appropriately British, featuring the Queen sitting at her desk in Buckingham Palace, opening one of her official red boxes, looking off to the side while Sir Paul McCartney's daughter Mary McCartney snaps the photo.
But aside from Her Maj having German heritage, there is something else discernibly German about the photo.
Her pink and white flowered dress was created by German designer Karl-Ludwig Rehse, who has been fashioning the Queen's royal garb for more than 25 years.
Karl-Ludwig Rehse. Photo: DPA
Born in Essen in 1937, Rehse's interest in fashion was sparked at an early age. After feeling inspired by a visit to a Düsseldorf craft fair with his grandmother, he started training to become a men's tailor, though he dreamed of creating women's clothes instead.
"I wanted to be a women's tailor, but the business association said men could not do that," Rehse told the Westdeutsche Allgemeine Zeitung (WAZ) in an interview last month.
He then worked in a boutique in Düsseldorf and later studied at a fashion school in Munich, where he began to tailor the wardrobes of aristocrats and movie stars.
"I actually wanted to work in Paris, but then it became London," he said.
After a visit to the British capital in the 1960s, he was hooked and decided to move there.
By 1988, he had started his own business with a friend and after a show of their summer collection that same year, Rehse got a call that he said changed his life: an invitation to show his work to the Queen.
"I was then presented to Her Majesty," he told Focus. "I was so excited, I think I was shaking."
Since then, Rehse has been a favourite designer of the Queen, who calls on him to devise her ensembles months in advance for events like her 60th Diamond Jubilee.
"I have to pinch myself sometimes," Rehse told Focus. "So long as Her Majesty needs me, I will continue on."
The Queen wearing an outfit by Karl-Ludwig Rehse during her Diamond Jubilee celebration. Photo: DPA