Prince William made a surprise guest appearance on Dancing With The Stars on Tuesday night

Ahead of his latest performance alongside his professional dancer partner Witney Carson, Robert told his sister Bindi Irwin - who won the 2015 version of the show - how he had made a huge sacrifice to continue with the series, because he was due to appear alongside William at the Earth Shot Prize in Rio de Janeiro, Brazil, last week.

However, he couldn't make it because he was still training for the show.

Robert and Witney then had to take a break from their dance preparations to receive a "special call", and he was shocked when the future King of England appeared on the line.

He asked William: "How was Rio?"

The Prince of Wales said it went "really well", and added: "We're missing you."

William then joked: "Whilst your twinkle toes are going off elsewhere, I need you down here."

He also told Witney to dress Robert in "as much glitter" as she could, and the pro dancer replied: "Listen, I'm trying."

The royal concluded his call by wishing the pair "best of luck" for the remainder of the series, and said they have a "seriously good chance of winning it".

A delighted Robert fell back onto a sofa following the call, admitting it meant "the absolute world".

Before his conversation with William, Robert explained he and Witney were dancing a Foxtrot to Leona Lewis' Footprints in the Sand, which was one of Bindi's performances during her triumphant Dancing With The Stars season.

She had dedicated the dance to her and Robert's late father, conservationist Steve Irwin, who died in 2006 aged 44.

Following his call with the prince, Robert said to Witney: "We are doing this dance for Bindi, and we're doing this dance for Prince William.

"So, let's not mess this up."

Following their royal seal of approval, Robert and Witney went on to score a perfect 40-out-of-40 score for their Foxtrot.