Harry, 39, made no mention of his father and his cancer diagnosis during his speech, which saw him hand out the Walter Payton Man of the Year award to Pittsburgh Steelers defnder Cameron Heyward.
Harry flew from Los Angeles to London on Monday evening after he was informed privately of his father’s diagnosis. He was later pictured arriving at Clarence House.
He then spent 45 minutes with the 75-year-old monarch before he returned home on Wednesday, having had no contact with his estranged brother Prince William.
The two have had a fractured relationship for a number of years, exacerbated after the Duke and Duchess of Sussex stepped down as working royals, moved to America and aired a string of grievances against the royal family.
In his first public appearance since Charles revealed he had begun treatment for an undisclosed cancer, Harry introduced the award and joked that the United States “stole rugby from us and you made it your own”.
“Instead of passing it backwards, just pass it forwards,” he said. “Why not wear pads and a helmet?
— NFL (@NFL) February 9, 2024
“All kidding aside, what you guys do on and off the field is truly remarkable. You are role models for millions in the way you carry yourselves and the way you give back.
“This final award, the highest honour, is all about serving your community, and there is one special man we’d like to pay tribute to now.”
When Heyward received the award, he hugged the duke, before he said: “Prince freakin’ Harry, I’m just shocked, that’s Prince Harry.”
The award recognises a player who has achieved on and off the field and made a positive impact on their community.
The winner is awarded 250,000 dollars (£198,000) to donate to a charity of their choice.
His appearance comes ahead of a High Court hearing on Friday morning which will hear how much side each should pay in costs, following the duke’s successful glaim against the Mirror Group Newspapers.
After a trial last June which saw him give evidence, he was awarded £146,000 in damages after the judge found that 15 out of the 33 articles were the product of unlawful information gathering or phone hacking.
In a previous hearing last month, Harry threatened to pursue a second trial against the publisher if he was not awarded appropriate damages.