She and husband Prince Harry handed a winner's trophy to Frankie Dettori.
The Duke and Duchess of Cambridge were guests at Ms Fellowes' wedding in Snettisham, Norfolk, in 2009, and with just a year between their ages, the Duke and Ms Fellowes often played together as children.
George was also christened in the Chapel Royal, but Charlotte was baptised at the Church of St Mary Magdalene in Sandringham.
The Chapel Royal is the same venue used for Prince George's christening on 23 October 2013.
Plane carrying Saudi Arabia's World Cup team catches fire
The second half was even scrappier, with Saudi Arabia too limited to run riot as Uruguay were happy with a narrow advantage. The Saudis continued to move the ball around but barely threatened the typically gritty Uruguay defence.
Here's everything you need to know about Prince Louis' big day.
Prince Louis' christening date has been confirmed by the Duke and Duchess of Cambridge, Kensington Palace said today. The Duke and Duchess of Cambridge will share photos but will keep the occasion as private as possible.
But the royal expert insisted the church where Princess Charlotte was christened is also close to the hearts of the royal couple.
Royal expert, Richard Fitzwilliams told Express.co.uk the choice showed Prince William's desire to have an "enduring link" to his late mother, Princess Diana. It will be the flawless opportunity to see the Cambridges out together in public as a family-of-five for the first time. Mental health has always been a priority for Prince William, Prince Harry, and Kate Middleton, who started Heads Together to tackle the stigma around getting help for mental illness.
The Duke and Duchess of Cambridge's youngest child, born on April 23, will be baptised in the Chapel Royal at St James's Palace in London.