Prince William leaves Robert Irwin blushing over racy comment about his 'python' during cheeky appearance on The Graham Norton Show

Prince William's appearance on The Graham Norton Show delighted his fans - and left Robert Irwin embarrassed. 

The royal and the Australian conservationist were both guests on the comedy chat show on Friday when the topic of Robert's racy Bonds underwear ad came up. 

Images from the shoot, which show Robert, 22, wearing nothing but underpants and posing with snakes and spiders, were shown during the episode. 

Robert was visibly blushing as William, 44, inspected the revealing images. 

'I can't believe I'm looking at these with Prince William,' Robert said, sounding coy and frazzled. 

'It was an underwear commercial, obviously, but I wanted to kind of create a conservation element to it,' he explained. 

'I believe in bringing the message to an audience that might not ordinarily be in that world.' 

The chat turned to the huge huntsman spider seen in Robert's advertisement, at which point William made a cheeky quip. 

'I'm still thinking about your python,' William joked. 

Robert responded with hysterics, looking decidedly red-faced as he tipped over and planted his face into the couch. 

The friendly banter between the pair continued when the Prince shut down the celebrity conservationist when he revealed he had named a 12-foot-long saltwater crocodile after him.

'We recently caught this beautiful 12-foot unit of a croc!' Robert began. 

'He was beautiful, death-rolling, he had teeth like this, he came out swinging, he was just amazing!'   

Robert revealed he had named the animal after one of his favourite people: the heir to the throne.

'It is Prince William the crocodile!' Robert said.

However, an amused William quickly shut it down, joking that the name didn't seem appropriate.

'It should have been named after The Rock... it shouldn't be me!' William joked.

Robert previously shared on social media why he had named his latest catch after the Prince of Wales.

'Meet "Prince William," a 12-foot 6-inch saltwater crocodile and the 300th crocodile tagged through our world-leading research project on the Steve Irwin Wildlife Reserve,' Robert shared in September. 

Robert and William have been friends for years, with the pair working closely together on animal conservation projects. 

In September last year, the Prince and Princess of Wales shared a sweet message to Robert, after he won Dancing with the Stars US.

William and Kate used their official Instagram page to praise the Australian conservationist, who took home the trophy alongside dancer Witney Carson.

Robert, who is an ambassador for William's Earthshot Prize, shared a video snippet of the grand finale on his Instagram page.

'Congratulations Robert and Witney!' a comment from the couple's account read, followed by a disco ball emoji.