Prince Harry was joined by Olympic cycling stars Laura Trott and Jason Kenny to watch the raucous finals of the women's beach volleyball, just a stone's throw from Buckingham Palace.
The 27-year-old is one of the sport's best-known fans after he famously took part in an impromptu game in Rio de Janeiro during a visit to Brazil.
He sat in the stands at Horse Guards Parade today with Trott, 20, and Kenny, 24, who both became double gold medallists at London 2012.
Footballer and Olympic ambassador David Beckham was also spotted among the spectators.
Harry was at the velodrome last night to see Trott, from Cheshunt, Hertfordshire, secure her second gold in the women's omnium, having captured her first medal just days earlier in the women's team pursuit.
Trott's cycling team-mate Kenny won gold in both the men's sprint and team sprint earlier last week.
Harry, wearing a blue polo shirt, was seated next to Trott, and was seen chatting and laughing with the cyclist.
The Prince visited Brazil in March this year as part of a campaign to promote the UK. During the visit he donned a number 11 top in Brazilian national colours for a three-a-side beach volleyball match.
On Harry's team was Brazilian Adriana Behar, one of the sport's most outstanding players.
The Prince watched as Behar's compatriots, Juliana Silva and Larissa Frana, beat the Chinese pairing of Zhang Xi and Xue Chen in the bronze medal match today.
Next up was the final between two teams from the USA, with Misty May-Treanor and Kerri Walsh Jennings beating April Ross and Jennifer Kessy.
Harry's appearance at the beach volleyball was no doubt a thrill for the American players.
Ross, 30, from California, earlier joked: "We've been tweeting Harry. I'd just like a photo opportunity with him."
May-Treanor, 34, said: "It's neat when you get delegates of other countries interested, travelling around to see the different venues. It's important."
The beach volleyball event has become a crowd favourite, with music, dance and audience participation creating a party atmosphere at the Whitehall venue.
The finals were no different, as fans got into the spirit with flag-waving, cheering and Mexican waves, as well as an interval performance by British pop star Mika.