The Traitors has always been a show about scheming, wild accusations and deceit, but the programme’s celebrity contestants face a fresh challenge: they will have to behave badly towards people they already know.

In the past three series, the show has brought together strangers who have to root out the “traitors” in their ranks while the “faithful” are being “murdered”.

Yet with The Celebrity Traitors, which launches on BBC1 on Wednesday night, some of the contestants will be forced to betray those they know, while others might find themselves falsely accusing an old friend.

“We have people in there that have a relationship outside the castle and that automatically brings a different dynamic which is fresh and a blessing in a way — like [contestants] Clare Balding and Tom Daley go back a long way,” said Lewis Thurlow, the executive producer. He added that knowing other contestants “could help your game, but it could also hinder your game, and cloud your judgment of that person. Once you set foot into that castle, everything you thought you know goes out the window.”

The Traitors, which is based on a programme created by the Dutch producer IDTV and made for the BBC by Studio Lambert, is filmed at Ardross Castle in the Scottish Highlands, near Inverness.

Contestants on the celebrity version include the actors Stephen Fry and Celia Imrie, the presenters Jonathan Ross and Kate Garraway and comedians including Alan Carr and Lucy Beaumont. The winner — or winners — will receive £100,000 for their chosen charity.

Although a long line of celebrity fans of the show were keen to be on the series, it is not the most glamorous job. There is no hair, make-up or wardrobe help, and the celebrities were cut off from their usual comforts during filming.

“The celebrities were treated the same as the regular contestants,” said Thurlow. “They were stripped of the usual comforts, luxuries and glam-squads — those don’t exist in Traitor-land and never will. It was actually a test of who really wanted to play the game. Stripping that away results in the brilliance of seeing them on screen with no distractions, and once the clock strikes midnight, just like in the regular series, they all get into the individual vehicles and go to their individual lodgings where they can’t speak to the others. There was no special treatment.”

Thurlow said that producers and casting directors looked for a similar quality in contestants for both the regular and celebrity series: a desire to throw themselves into the game.

“We want people there for the ‘right reasons’, whether it’s celebrities or civilians,” he said. “Their passion comes through on screen; we want the audience to watch the celebrities and think ‘they’re really into this’. They’re all fans of the show for different reasons — Celia, for example, was just in The Thursday Murder Club and has a love for that [solving mysteries]. We could ask the biggest celebrity in the world, but we only want them if they are passionate about the game.”

A major difference between the main series and the celebrity version, however, is that non-famous contestants often hide the fact they have acted in the past, fearing that it will put them under the spotlight of suspicion, whereas well-known thespian contestants cannot disguise their careers. Thurlow said that being an actor was not necessarily an advantage.

“You assume they’re going to be good because they’re actors, but what you think about people totally changes as you watch it,” he said. “The people you’d think would be amazing at lying are often not. I don’t think being an actor can really prepare you for the twists and turns that will ultimately happen, because you have to think so quickly on your feet, and maybe an actor would have to work harder at making sure people trust them.”

When the crew were making the first Traitors series, Thurlow recalled that they would often fantasise about who would be on their dream celebrity cast.

“We’d joke about ‘can you imagine if so-and-so and so-and-so was playing this game’, thinking about celebrities as if one day it would actually happen, and then when it actually got commissioned, some of them did end up in the castle,” he said. “Obviously I can’t name names, but … seeing them all for the first time in the castle together was such a special moment. You can’t believe that this person is talking to this person about the game that you kind of created.”

Despite the show’s popularity, Thurlow said that he still felt great pressure to deliver another hit series. “We always get nervous just because we love it so much and we want other people to keep loving it,” he said. “We have so many committed fans and you want to keep them entertained and happy. But ultimately, you just have to trust the game, trust you’ve got the right mix of people playing, sprinkle in the twists and turns, and it’s a pretty magic formula — you don’t want to mess with it too much.”

The Celebrity Traitors airs at 9pm on Wednesday on BBC One