The Prince of Wales presents England captain Luke Tomlinson with the winners' trophy Audi International Polo featuring the Westchester Cup, at Guards Polo Club in Egham, Surrey
The Prince of Wales was mobbed by well-wishers congratulating him on the birth of his first grandson as he attended the polo today.
Hundreds of people swarmed around The Prince when he went onto the field at half time during the Westchester Cup, the sport's answer to the Ryder Cup.
He shook the hands of many spectators who came forward to congratulate him on the birth of his grandson Prince George of Cambridge, when he joined them for the tradition of going onto the field of play to stamp down divots made by the horses.
An area was roped off in front of the royal pavilion at the Guards Polo Club in Windsor Great Park, where he had previously watched the first three chukkas between England and the United States.
But in a surprise move, The Prince stepped over it and walked into the crowds.
Kevin Newberry, 36, from Oxford, was one of those who shook hands with The Prince.
"I just went up to him and said 'Congratulations', and he replied 'thank you very much'," he said.
Joining The Prince in the Royal pavilion at the game were celebrities including Star Trek actress Alice Eve, Strictly Come Dancing's Brendan Cole, Life on Mars stars John Simm and Philip Glennister, and television presenter and former England rugby union scrum half Matt Dawson.
The Prince presented the Westchester Cup, the sport's oldest trophy, to the England team after they beat the United States 12-11 in the first chukka of extra time.
It was the first time the competition had been held in England since 1997, but the hosts were the holders, having beaten the Americans the last time they met in 2009.
David Wood, the Chief Executive of the Hurlingham Polo Association (HPA), said they had been pre-warned that The Prince was planning to go walkabout on the field of play at half-time.
"I think everyone here is thrilled, they are great supporters of him and the family," he said.
"I think they are all delighted, it's great news.
"I hope the baby will be a polo player when he grows up, I'm sure he will be."
The four-man England team included Mark Tomlinson, who plays polo with The Duke of Cambridge and Prince Harry.
The Duke and Duchess of Cambridge attended his wedding to London Olympics dressage gold medallist Laura Bechtolsheimer in the Swiss Alps in March.
After the game, Mr Tomlinson said he had joked with The Prince about the baby's arrival and how his friends were dealing with parenthood.
He described the English victory as "a great moment" and joked that it was good that unlike the England football team, they had not had to try to win on penalties.