The Prince and Princess of Wales joined 20,000 basketball fanatics to cheer on the Boston Celtics and promote the Earthshot Prize awards on their first day in the city.
William and Kate were brought into the TD Garden stadium to sit court side and watch the action alongside the Celtics owners Wyc Grousbeck and Emilia Faszalari alongside Govenor elect Maura Healey and Boston Mayor Michelle Wu.
Kate and William stood for the national anthem The Star Spangled Banner which was belted out by a semi finalist of season 10 of reality tv series The Voice.
But later the royal couple were subject to small pockets of boos around the arena when they were introduced by a stadium announcer and shown on the big screen.
The Boston Celtics’ name was inspired by the Original Celtics, a well-known basketball team that had been created by Irish immigrants in New York earlier in the 20th century, before folding in 1930.
Others fans in the crowd could be heard loudly cheering “USA, USA” when the Prince and Princess appeared on the screens in the centre above the court.
The royal couple were seen cheering the high scoring game and clapping points as the packed crowd ramped up the atmosphere for the seventeen-time World Champions took on the Miami Heat in downtown Boston.
During several intervals in the game there were moments nodding to the arrival of Prince William’s Earthshot Prize environmental project which will be hosted in the city on Friday.
Before the game tipped off the royals met members of the ‘Celtics family’, including representatives of the Boston Celtics Shamrock Foundation, which provides grassroots programming and strategic funding to local organisations serving at risk or at need populations.
Around the stadium digital advertising boards were lit up green to promote the awards while spectators were treated to a promotional Earthshot video ahead of the game.
After the second quarter with the game tied 47 all William and Kate watched as the Celtics honoured their long standing tradition of recognising a “Hero Among Us”, heralding individuals working to positively impact the community.
Ollie Perrault, a 15-year-old climate activist from Easthampton, Massachusetts, got to meet the royal pair after being cheered by the local crowd for her work as a leading member of the Youth Climate Leadership Program since she was 11.
She is now the founder and director of Youth Climate Action Now, committed to fighting for environmental justice, advocating for an intersectional system change, and working to get more young people involved in direct climate action.
Royal aides suggested the royal couple would depart after the third quarter of the game but they decided to stay until the end, shaking hands with fans as they left.
The royal couple arrived in the United States on Wednesday for a three-day trip before he attends the Earthshot Prize ceremony on Friday, an award he founded to celebrate contributions to sustainability.
The visit to the United States for the prize is their first overseas engagement since becoming Prince and Princess of Wales in September.
The Earthshot tour has been overshadowed after William's godmother and senior courtier Lady Susan Hussey was forced to resign over comments to a black woman that have rocked the monarchy.
Ngozi Fulani, who was born in the UK and runs a black women's domestic abuse charity, said the royal aide asked her: "Where do you come from?"
In a conversation that followed, Hussey continued to ask "what nationality are you?", "where do your people come from?" and "what part of Africa are you from?"
Buckingham Palace released a statement condemning the "unacceptable and deeply regrettable comments" and confirmed she had "stepped aside from her honorary role with immediate effect."
Ngozi told the Mirror: "[What she did] was racism. Through and through. It was prolonged racism.
"The fact that it was just done in the open in front of people, on a day when we should be working towards violence against women."
Ngozi also said Hussey told her: "I can see I am going to have a challenge getting you to say where you're from. When did you first come here?"
Eventually, Ngozi says she replied: "I am a British national, my parents came here in the 1950s," before Hussey responded with: "Oh, I knew we'd get there in the end, you're Caribbean."
Ngozi says she then corrected the aristocrat by responding with: "No, I am of African heritage, Caribbean descent and British nationality."
