Dressed in a dusky pink lace dress, Geri stood arm-in-arm with her Formula One boss love Christian, who sported a black blazer, beige trousers and suede shoes.
Geri and Christian made their first public appearance since getting engaged
Former Spice Girl Geri, who has been dating Christian since March, proudly wore her new diamond ring on her left hand.
The bride and groom-to-be joined Prince Harry, Sir Philip Green and Sir Jackie Stewart at the sporty event. Prince Seeiso of Lesotho, who set up Sentebale with Prince Harry in 2006, was also present at the match.
Geri and Christian announced their engagement in the same traditional way that Benedict Cumberbatch and his fiancée Sophie Hunter chose to – in the Births, Marriages and Deaths section of The Times.
The couple were seated with Prince Harry at a dinner following the polo cup
"Mr C.E.J. Horner OBE and Geri Halliwell," read the listing. "The engagement is announced between Christian, son of Mr and Mrs G.M. Horner and Geraldine, daughter of the late Mr L.F. Halliwell and Mrs A Parkinson."
Geri, 42, and Christian, 41, both have children from their previous relationships. The singer is mum to eight-year-old daughter Bluebell with Sacha Gervasi.
Christian, meanwhile, recently split from his partner of 14 years Beverley Allen, with whom he has a one-year-old daughter Olivia.