Prince William presented 150 medals ahead of Buckingham Palace's first ever football match, which took place on Monday afternoon.
When he was giving the awards to the grassroots volunteers in recognition of exceptional service to the sport, William quipped: "You will be playing football on my grandmother's lawn. One warning, though: if anyone breaks a window, you answer to her."
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Jokes aside, the new dad, who is president of the Football Association and hosting the match as part of the celebrations to mark the FA's 150th anniversary, welcomed his guests with a sincere speech.
"This magnificent home, Buckingham Palace, is at the heart of the nation, and so there cannot be a more fitting setting to celebrate our national game, and to celebrate all of you," William said.
"At its best, football is a powerful force for good in society. It binds people from different backgrounds, communities, faiths and abilities – and gives them a common interest, a unifying identity.
I believe over its 150 years, football has remained a wonderful example of the power of community and of our ability to come together to organise and to enjoy a simple pastime."
The game saw the palace lawn become the world's most exclusive football pitch when two of England's oldest amateur clubs played in the unique Southern Amateur League fixture.
Civil Service FC played against their local rivals Polytechnic FC in the game, for which Prince William asked permission from his grandmother the Queen.
Her Majesty was at Balmoral while the grounds of the palace were opened for the special occasion. William said that "Her Majesty...sends her regrets that she cannot join you today."
He added: "The one small silver lining to Her Majesty not being present today is that there shouldn’t be any corgis running on to the pitch."
Wembley groundsman Tony Stones worked with the royal household gardeners to create a pitch in the 40-acre gardens of the famous landmark.
Markings for the pitch – measuring 100m by 60m – began last month and have been mowed with criss cross stripes, just like those at Wembley.