The scene is suitably dramatic: the turreted Ardross Castle, an impressive 19th-century baronial-style fortress located in the Scottish Highlands. Here, the first Celebrity Traitors are ready to huddle in shadowy corners, backstabbing and whispering, as they bid to unmask the betrayers in their midst. Because, yes, filming for the first star-studded version of the BBC favourite, hosted as ever by Claudia Winkleman, began this week. Planning for the celebrity version of the show had been extensive to say the least, with TV bosses using every trick in the book to ensure their line-up remained top secret until the programme aired in the autumn. I'm told that getting the celebrities to Scotland has been 'a military operation', with bosses desperate to conceal their identities for as long as possible. The cast travelled north individually, using a variety of transport, including planes, trains, cars and even boat to ensure their paths didn't cross – just in case passing members of the public put two and two together and worked out where they are heading. Production managers have even been granted permission by aviation officials for a 'no fly zone' above the castle, to prevent drone photographers securing behind-the-scenes images. Yet, despite the diligent preparations by BBC bigwigs, all, it seems, has come to naught. For already the entire celebrity cast of 19 – which includes Stephen Fry, presenter Jonathan Ross, diver Tom Daley and actress Celia Imrie – has been leaked to the press. And yesterday, in scenes which made something of a mockery of those elaborate travel plans and drone banning orders, some celebrities were seen touching down at Inverness Airport. Sir Stephen arrived in Scotland alongside an aide, as did Daley and Ross, who were seen wheeling suitcases into waiting cars. Also spotted was Brit Award nominee Cat Burns who did her best to hide her identity behind a huge pair of sunglasses, while singer Charlotte Church stood out in distinctive green and white striped pyjamas. Singer and actress Paloma Faith was also spotted, as was Irish actress Ruth Codd, star of Netflix series The Midnight Club. The group then headed to the castle to begin filming. Pictures of these arrivals, captured by a top paparazzi firm, are likely to enrage BBC bosses further. Indeed, I can reveal that more than 400 miles away in London, senior Corporation figures and the bosses at Studio Lambert, the production company that makes the programme, have already been locked in crisis meetings after launching their own probe into who their traitor is. Show insiders describe bosses at both organisations being 'increasingly furious', as well as 'panicked' and 'bewildered' after realising there could be someone working within their networks leaking confidential information. How else, they wonder, could names of the line-up seep out almost daily, long before they had wanted them to? I can also reveal that the show's bosses are so infuriated they've spoken to someone they're told could be responsible. There have been discussions about involving lawyers, but the source of the leaks cannot yet be pinpointed with certainty. So concerned is the BBC about this, that acting chief content officer Kate Phillips, its most senior television executive, has been front and centre of attempts to manage the furore. One show insider tells me: 'There's been much panic in recent days, with flurries of phone calls, and discussions between the BBC and Studio Lambert. Of course, things leak out all the time, but the entire line-up has come out and been printed. 'Legal action has been talked about. It is crisis time. Not only have they not been able to keep the details out of the public eye as they had hoped, but the information seems to be coming faster than ever before and with astonishing levels of insight. 'Kate and the rest of the team are furious about what has happened, and behind the scenes are doing everything to find out who their mole might be and why they would want to do this. 'They're begging the press to stop the leaks, too. There's every possibility somebody on the show is doing it for their own financial gain – it seems the only explanation – but it would be a huge breach of their contract and they'd risk being dismissed immediately if caught. They're playing with fire, and now that the top bosses are onto it they could find themselves in some very serious trouble. It will certainly be a bombshell moment if and when their identity becomes clear.' Leaks continued even after April 17, the day Kate Phillips wrote to the media begging them not to reveal any more secrets about the programme. Ms Phillips penned the letter, along with Stephen Lambert, CEO of the show's production company, which was sent to journalists – including me. She wrote: 'Given the nature of the show, we love to surprise our viewers, and by keeping every twist and turn under wraps we feel it really adds to the magic of The Traitors. We ask you to refrain from engaging in spoilers so as not to ruin the series for your readers. 'When we do begin filming we hope for a respectful distance, but realise there may be candid snaps captured by members of the public, comments on social media, enterprising independent photographers and agencies seeking to get a show – but we'd ask that you don't promote anything captured in this manner. We realise that due to your excellent connections, over the coming months you may be privy to information.' She went on to list the elements they hoped to keep secret, including the show's line-up, the order of eliminations and any photographs from the set captured by onlookers, concluding: 'We are hoping that with your help, we can keep the line-up under wraps until the time is right.' Ms Phillips and Mr Lambert also asked that the press did not use any photographs paparazzi agencies might have captured, in a further bid to maintain the secrecy for their viewers' enjoyment. The same day that their pleading letter was sent, it was reported by The Sun that Channel 4 comedian Joe Wilkinson, best known for his role in 8 Out Of 10 Cats Does Countdown, had joined the line-up. And the following day Cat Burns was unveiled by the same paper. The full line-up was then published by The Sun for the first time this week. It also includes Line Of Duty actor Mark Bonnar, Good Morning Britain host Kate Garraway, comedian Alan Carr, sports presenter Clare Balding, Ted Lasso star Nick Mohammed, England rugby union prop Joe Marler, comedian Lucy Beaumont (ex-wife of Jon Richardson), historian David Olusoga, YouTuber Niko Omilana and EastEnders actress Tameka Empson. Bosses at both the BBC and Studio Lambert are said to be 'thrilled' with the line-up, which they have been slaving over for some months. One show insider said: 'There has been so much pressure for this all to be kept quiet. 'The letter went out from a really senior boss, yet there is someone who is believed to be involved with the BBC or the show who has been putting this information out there. It's a joke. Someone really is taking the mickey out of Kate and Stephen. After all, it's amazing to work on a show like Celebrity Traitors.' In short, it's an utter embarrassment for the BBC that its biggest new entertainment smash – ten million viewers tuned in for the third series finale of the regular version in January this year – has been so quickly tarnished. The show format sees a group of hopefuls attempt to persuade their fellow competitors that they are 'Faithful', while three are secretly chosen to be 'Traitors'. With contestants eminimated at the end of each episode, the final few battle it out for a share of a cash prize worth up to six figures that has been accumulated during the series. Winners have gone on to achieve further fame, with series two winner Harry Clark appearing on BBC Two show Pilgrimage, while runner-up Mollie Pearce took part in ITV's Dancing On Ice this year. For Ms Phillips, the leaks are something of a personal embarrassment, too. She is currently acting up from her role as director of unscripted, to which she was appointed in 2022. Her temporary promotion to chief content officer came after news in February that Charlotte Moore was to leave the role to move to Left Bank Pictures and Sony Pictures Television. Ms Phillips, one of BBC director-general Tim Davie's most loyal lieutenants, is in contention to get the job permanently, and Celebrity Traitors would be her first huge triumph. Indeed, the UK celebrity version is predicted to be even bigger than previous series – with bosses confident it can become one of the most watched TV shows of the year. However, as one BBC insider said: 'Kate is a great woman, someone who is hugely respected at the BBC, but after the letter she sent this is just embarrassing. Woe betide the person who has been leaking all this when she finds out who they are.