Meghan, Duchess of Sussex, was said to have pocketed up to $380,000 for her top-secret appearance on MasterChef Australia - but the truth is even more astounding.

The Daily Mail can reveal Meghan was not paid a cent, and didn't even promote her As Ever food and lifestyle range, featuring flower sprinkles, fruit preserves and wine. 

The 44-year-old quietly visited the set of the reality TV cooking series on Wednesday to film her show-stopping segment at Melbourne Showgrounds.

It is understood she was on set for the entire day of filming, with Network 10 later confirming she would be a guest judge in an episode of the new season.

Some TV industry analysts initially suggested she could have been paid up to US$250,000 (AU$380,000) to appear on the show.

Former TV executive Rob McKnight dismissed the six-figure fee, but revealed the Duchess could easily have demanded between $10,000 to $50,000.

'I think it is a brilliant PR move by Network 10, which is probably worth the least amount of money of the major networks,' he said hailed the publicity coup.

'It has shown Ten is the little engine that could.'

'Having Meghan in the MasterChef kitchen with us was such a treat,' MasterChef Australia judges Poh Ling Yeow, Sofia Levin and Jean-Christophe Novelli told the Daily Mail.

'She was a complete delight and was right at home. Introducing her to the contestants was like the best kind of surprise party - jaws were on the floor! 

'The Duchess put us all at ease very quickly, learning about our home cooks through their food, and happily sharing her passion and knowledge for produce, cooking and entertaining with us all. We'd have her back in a heartbeat.'  

Meghan and Prince Harry are in Australia on a whirlwind tour, mixing royal-style engagements with commercial enterprises, including paid speaking events. 

Meghan is not the first royal to appear on MasterChef Australia, and has followed in the footsteps of her father-in-law King Charles and his wife Queen Camilla.

In 2018, during an official royal tour, the then-Prince Charles and Camilla, then the Duchess of Cornwall, appeared on an episode filmed in Darwin. 

The royal couple drew criticism online for not being filmed eating the contestants' bush tucker, which included wallaby tartare with green ants. 

Meghan's appearance on the show has divided fans before it even goes to air. 

But McKnight said MasterChef bosses would not be upset by the response from fans.

'Here's the thing,' he said. 

'The backlash against Meghan Markle doesn't hurt.

'It's got everyone talking about the show, and before this, how many people knew it was coming back? It's been so off the radar. 

'Meghan polarises people. People love her, but a lot of people hate her, which means she is far from boring.'

'MasterChef Australia is currently in production and this week's very special episode featuring Meghan, Duchess of Sussex, was filmed as part of the regular schedule and featured Season 18 contestants,' a Ten spokesperson said.

'Viewers will share in the experience when the episode airs later this season. Stay tuned for the season premiere of MasterChef Australia this Sunday at 7pm on 10.'

Meghan and Prince Harry landed in Melbourne on Tuesday, when they arrived in the Victorian capital having flown business class from Los Angeles on a commercial Qantas flight.

As well as Meghan's top-secret MasterChef appearance, the couple visited the Royal Melbourne Children's Hospital, McAuley Community Services for Women in Footscray, and the National Veterans Art Museum. 

On Thursday, the couple also attended mental health-related events and met with Indigenous elders on Melbourne's Scar Tree walk.

The couple are in Sydney on Friday for a packed schedule including a harbour sail with Invictus Australia, Meghan's hotly anticipated Q&A at a women's retreat in Coogee, and attending a rugby union match.