When the cameras start rolling on Celebrity MasterChef, the contestants may be the ones sweating over the stoves, but there is plenty going on behind the scenes.

The 21st series has a new judging partnership at its heart, with chef Giorgio Locatelli joining food critic Grace Dent.

Dent said that filming, which takes place at Birmingham's Digbeth Loc Studios, could last for 12 or 13 hours a day, with cameras rolling continuously.

"I'd love to come here with a character and go, 'this is how I'm going to come across', but I don't think you could keep it up for very long," she said. "They're filming continually and I don't have any control over how they cut me, so really you're just getting the real me."

Dent has been based in Birmingham for a year and said she felt "like a part of the furniture" in the city.

"I do live here most of the time," she said. "I love Birmingham, I love the shopping, I love the people.

"I never feel lonely in Birmingham, because there's always someone that wants to talk to me, and once you get talking, it goes on and on because people love a little gossip."

Despite being a long way from home, Italian chef Locatelli said the city was "very welcoming", adding that living in the city's Jewellery Quarter was "really, really nice".

"The people are happy to have a chat with you and tell you about themselves, and so that fitted very well," he said.

His only complaint was about the British winter, which he said was "a killer".

"We got up in the darkness and rain and then we went back in the darkness and rain in the night," he said.

Both judges praised their workplace at Digbeth Loc.

"We are in this fantastic purpose-built building with this incredible studio," Locatelli said. "They've got a really nice space for us."

Dent added that the studio was a "complete treat" and was "busy all year round" with MasterChef filming.

The pair, who had been working together for the first time, said they were initially "a bit shy" around each other.

Locatelli had come straight from MasterChef Italia, while Dent was already established on the British version.

But as they got to know each other, Dent, who is originally from Cumbria, said she made Locatelli laugh and joked that her northern accent had begun to infiltrate his Italian one.

The judges said they deliberately took different approaches to scrutinising contestants' food.

Locatelli approaches dishes from the perspective of a chef, looking closely at technique and execution. Dent brings her experience as a critic, considering the wider story behind what is on the plate.

Locatelli said having two perspectives meant they could examine food from "360 degrees".

He also said he had learnt a lot about food from Dent, particularly Indian cuisine, which is central to Birmingham's culinary scene.

Locatelli said one of the biggest differences between MasterChef in the UK and Italy was the range of influence on British plates.

While MasterChef Italia is deeply rooted in the country's own food traditions, he said the British version featured a much broader mix, including Indian, Japanese and Mexican influences.

For the judges, hours spent watching contestants cook also reveal something beyond culinary ability. Locatelli said food could expose a person's character.

Contestants might arrive determined to present a polished version of themselves, but after spending hours under pressure, their real personalities begin to emerge.

"You can actually see what he's thinking, where he's coming from," Locatelli said.

That can be particularly entertaining on the celebrity version of the show.

Dent said some of the celebrities arrived with very little cooking experience and were just there to have fun. Others became increasingly serious as the competition progressed.

Celebrities also have another skill to bring into the kitchen: performing.

Dent said she had seen contestants dress up, sing and dance in the studio.

This year's contestants include Olympic medallist Emily Campbell, broadcaster Jason Mohammad, comedian Joe Pasquale, TV personality Shakira Khan and musician Jay McGuinness.

The celebrities will compete across three heats, with four from each heat progressing to the quarter-finals.

Paddy McGuinness, Zoe Ball and Morgan Burtwistle, better known as Angry Ginge, will each appear as guest judges, setting the celebrities bespoke challenges.

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