Prince Charles Reveals Final Conversation With Prince Philip

A new documentary about the late Prince Philip is coming to BBC, and his family opened up about his last days in new interviews. Prince Philip: The Royal Family Remembers is set to air on Sept. 22 on BBC One, and in one of the interviews Prince Charles opened up about his last conversation with his father before he passed on April 9 at the age of 99. "We're talking about your birthday," Prince Charles emotionally admits in the interview.

Charles explains that at his advanced age, Philip was quite hard of hearing, so he had to repeat himself louder. "We're talking about your birthday! And whether there's going to be reception!" Philip had a characteristically dry response: "Well, I've got to be alive for it, haven't I?" Charles ruefully replies "I knew you'd say that!"

Prince William also shares a funny story about his time with his grandfather. They were out on the Queen's Balmoral estate and came across a group of young people walking, and Philip decided to speak to them. "He stopped and wound down his window and said, 'Good morning. How are you getting on?'" William says. "To which the smallest young chap at the back turned round and effectively said, 'Jog on Grandpa!'" Philip found the Interaction hilarious, telling William, "The youth of today!"

Even Prince Harry participated in the documentary, recoding his part from California, remembering Philip for always being "unapologetically him." He also praised his grandfather for being so supportive of his wife, the Queen. "From my grandmother's perspective, to have someone like that on your shoulder for 73 years of marriage – it doesn't get better than that," he pointed out. 

Kate Middleton and Prince William gave an update back in August on how they're doing following the death of Prince Philip. A letter that was received as a response to a condolence message revealed the royal couple's gratitude for the many messages they've received since Philip passed in early April. Gert's Royal Replies shared the reply where the Duke and Duchess of Cambridge thanked those who have sent them loving words through the difficult time.

"The Duke and Duchess of Cambridge thank you for your kind words following the death of The Duke of Edinburgh," the note reads according to PEOPLE. "Their Royal Highness have been incredibly moved by the many thoughtful messages they have received in recent weeks. They will all miss their much loved grandfather and great grandfather, but your message has provided great comfort at this difficult time."