Princess Eugenie, the granddaughter of Queen Elizabeth, was married on Friday in the UK's second royal wedding of the year.
Eugenie, 28, the second daughter of the Duke of York, married Jack Brooksbank, 32, at Windsor Castle, following in the footsteps of her cousin Prince Harry and his wife Meghan in May.
The Queen and Prince Philip attended the 15th century St George's Chapel alongside Eugenie's mother, Sarah Ferguson, and her sister Beatrice, to see the couple married by the Dean of Windsor, David Conner.
Princess Eugenie, a director at London's Hauser & Wirth art gallery, and Mr Brooksbank met in the Swiss ski resort of Verbier in 2010.
Mr Brooksbank is a son of an accountant. He skipped university and delved into a career in hospitality. He had a stint as the manager of the London nightclub Mahiki, once-popular with young royals and much of the British capital's creative set who were in attendance. He is also described as the "UK representative" of George Clooney's Casamigo's brand.
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The castle in Windsor, about 40 kilometres west of London, was also the venue for Harry and Meghan's wedding in May and Eugenie, ninth-in-line to the throne, copied much of her cousin's blueprint for her big day.
Charity guests and 1,200 members of the public were invited into the castle grounds for the occasion. The queen will host a champagne luncheon for the newlyweds shortly after the ceremony.
One noticeable absentee was Camilla, the Duchess of Cornwall, the wife of heir-to-the-throne Prince Charles, as she was carrying out an engagement in Scotland.
While Harry's wedding featured a fiery sermon from an Amnerican Episcopalian bishop and a gospel choir, Eugenie's was traditional, with a performance by Italian tenor Andrea Bocelli and the address given by the Dean.
Her elder sister Princess Beatrice was maid of honour and delivered one of the readings, an extract from The Great Gatsby.
Earlier in the morning, singing and cheering well-wishers gathered in the streets of Windsor in the shadow of the castle, although there were far fewer people than crammed into the town for Harry's wedding.
"There's not so many here as I expected," said David Weeks, 77, wearing a "Union Jack" suit and bowler hat.
"I'm a true royalist. I was here for the queen's 90th birthday. I was here for Harry and Meghan's wedding, I wouldn't miss it, I love the atmosphere."
Security around Windsor was tight, with the public having to pass through airport-style security checks to get near the castle and large numbers of police on patrol.
A smattering of celebrities were among the guests, with the daughter of singer Robbie Williams one of the bridesmaids.
Princess Charlotte, 3, daughter of Harry's elder brother Prince William and his wife Kate, was also a bridesmaid while her brother Prince George, 5, was a page boy.
After the service, the couple embarked on an open-top carriage tour of Windsor, although shorter than the one Harry and Meghan, now the Duke and Duchess of Sussex, took when thousands lined the streets of the town.
Queen Elizabeth was then to host a reception for the couple and their guests at the castle.
As Eugenie does not carry out official royal duties, republicans and some newspapers have said it is wrong that the estimated £2 million (Dh9.7 million) security bill for the event will be paid for by taxpayers, with the royal family only paying for the wedding itself.
Britain's Princess Eugenie wore an elegant voluminous dress by London-based label Peter Pilotto for her wedding to Jack Brooksbank, with the bride picking a low back to reveal scars she got from surgery as a child.
The 28-year-old granddaughter of Queen Elizabeth walked down the aisle of Windsor Castle's 15th Century St George's Chapel in a fitted corset and pleated skirt with a long train designed by Peter Pilotto and Christopher De Vos, who founded the label in 2007.
"The dress features a neckline that folds around the shoulders to a low back that drapes into a flowing full length train," Buckingham Palace said in a statement.
"The low back feature on the dress was at the specific request of Princess Eugenie who had surgery aged 12 to correct scoliosis."
Eugenie, who announced her engagement in January, worked closely with Pilotto and De Vos for the bespoke dress, with the designers leafing through archives of frocks worn by British royals to pick a silhouette.
Motifs meaningful to the couple were woven into a jacquard of silk, cotton and viscose blend, the palace said. The designs included the thistle and shamrock, the flowers of Scotland and Ireland, and the English rose.
Eugenie borrowed the queen's Greville Emerald Kokoshnik tiara, decorated with rose cut diamonds and emeralds and made by jewellers Boucheron in 1919 in the style worn in the Russian Imperial Court.
She wore diamond and emerald drop earrings given to her by Brooksbank and satin peep-toe heels by Charlotte Olympia.
Speculation over who would design the wedding dress had mounted over the last few weeks, with labels such as Erdem, Ralph & Russo among those mentioned in media reports.
"As soon as we announced the wedding, I knew the designer, and the look, straight away," she was quoted as saying. "I never thought I'd be the one who knew exactly what I like, but I've been pretty on top of it."
Eugenie, who works in art and Brooksbank, who is European brand manager for Casamigos Tequila, a brand co-founded by Hollywood actor George Clooney, married at the same venue that her cousin Prince Harry and Meghan Markle chose for their nuptials in May.