Prince Andrew crowed that the venue had to be St George's Chapel, Windsor, because the bride and groom have so many friends.
And a significant number of the guests were showbusiness celebrities. So how on earth do they all know Eugenie?
Kate Moss and Nikolai Von Bismarck: Kate Moss calls Fergie "The Duch". The pair got to know each other on the St Moritz ski scene. Eugenie knows Kate's boyfriend Nikolai, too. She and Beatrice were seen at parties with him before his romance with Kate began in 2015.
Artist Tracey Emin has been in Eugenie's inner circle of friends for five years but their friendship really blossomed during Eugenie's New York period, when both were living in the city.
Old Etonian Ollie fell into Eugenie's social circle when she was dating his close pal Hugo Taylor in 2008. He is now an Instagramming lifestyle blogger and is said to have built up a £5 million fortune. His fiancee Emma Louise Connolly cut a striking figure in red.
Eugenie introduced 'Cressie' to Prince Harry — a romance which came close to ending in marriage. Cressie seems to have originally been one of Eugenie's Verbier ski pals.
The Delevingne sisters:
Cara and Poppy Delevingne's mother Pandora was at school with Fergie and is one of the Duchess's life-long friends, counselling her as her marriage to Prince Andrew broke up. Their daughters are close.
Robbie Williams and Ayda Field:
Fergie became close to Robbie and wife Ayda during a holiday on a yacht owned by Phones 4U tycoon John Caudwell in 2011.
The comedian knows Eugenie via a friendship with her sister Beatrice — he and Bea are so close that they have holidayed together.
The singer met Eugenie at a nightclub in Ibiza where she was propping up the bar with mutual pal Jade Jagger in 2009. Eugenie was among those who attended his wedding in 2014 to society beauty Lady Sofia Wellesley.
Sharon Osbourne apparently introduced Fergie to Demi when she got both women — and their children — in to watch the X Factor in 2004
Nick Candy and Holly Vallance:
Property tycoon Nick is among Fergie's wealthiest friends and comes to her charity events. Eugenie bumps into Holly at various charity dinners in London, too.
National treasure Stephen Fry attended the wedding with husband Elliott Smith. He's yet another friend of Fergie's. He and Eugenie were regulars at socialite David Tang's Christmas party.
The TV presenter got to know Eugenie on the party circuit.
"We have a lot of friends in common," he said.