The couple are known for being discreet in front of the camera and follow in the Queen and Prince Philip's footsteps when it comes to public displays of affection. 

But the couple were surprisingly tactile in a rare loved-up display. 

After they were awarded their Gold Blue Peter badges, pregnant Kate put her hand on her husband’s knee as they thanked the presenters for being awarded their highest accolade. 

Prince Harry and wife-to-be Meghan Markle are often photographed showing their affection towards each other by holding hands and hugging.

However, Prince William is heir to the throne and so must be more careful about his etiquette towards his wife. 

The badges were awarded for the royal couple’s campaign work around mental health and issues affecting mental health issues. 

The Duchess of Cambridge was wearing a festive, red jumper dress with black heels and the Duke of Cambridge wore a suit for the occasion. 

The Queen was also awarded a Gold Blue Peter badge during her Golden Jubilee year in 2002.

Other people who have been honoured enough to receive the badge are David Beckham, JK Rowling and Tom Daley. 

When they received the badges from presenters Radii Chiny and Lindsey Russel, the Duke of Cambridge said: “That’s very touching. Thank you very, very much.

“Wow, that’s amazing. We have won a badge.” 

Referring to their work on mental health, Prince William added: “We’ve still got a long way to go but we are getting there.

“A shift is happening and we will hopefully crack a problem that should have been cracked a long time ago.”

He said he would have to “compare” badges with his grandmother, the Queen. 

The Duchess of Cambridge said: “It’s hugely special.

“Mental health has been a learning process. We want to get everyone talking about it so it hasn’t got that stigma it’s had.” 

Viewers can watch the Duke and Duchess of Cambridge being presented with their badges on Thursday’s live Blue Peter Christmas Special at 5:30pm on CBBC.