Celebrity SAS: Who Dares Wins is set to make its return next week, with a host of new stars taking on brutal quasi-military training. 

But it all proved to be too much for one actor, who quit the reality programme just two hours in.  

John Barrowman left the series after a tour of the accommodation and never it past the camp, fellow contestant Rachel Johnson has revealed. 

The sixth series will see celebrities take part in SAS winter warfare training in the south islands of New Zealand.

Contestants are not eliminated and are instead culled by the directing staff or able to withdraw themselves, with those who remain at the end declared the winners.

Speaking ahead of the show to MailOnline and other press, Rachel, 59, who is the sister of former Prime Minister Boris Johnson, said: 'John left like two hours in. 

'He did the first day and then he voluntarily withdrew in camp. When we were doing the tour of the accommodation.'

The Torchwood stars exit comes amid the news that Louie Spence also reportedly quit filming after just 24 hours. 

The choreographer, 55, is said to have been shocked at how the gruelling the process was and walked away, reports The Sun.

Louie was reportedly 'unable to keep up with the regime physically and mentally' - as he took on the challenge alongside the likes of reality stars Pete Wicks and Chloe Burrows. 

Rachel will be joined by Reality TV Star Bianca Gascoigne, former England rugby captain Chris Robshaw, TV Presenter Cherry Healey, former professional boxer Anthony Ogogo, comedian Shazia Mirza, former Love Island contestant Georgia Harrison, reality star Bobby Norris, and influencer Marnie Simpson.

The line-up will be completed by former Olympic gymnast Ellie Downie, comedian Tez Ilyas, professional basketball player and former Love Islander Ovie Soko, and World Heavyweight Champion boxer Lani Daniels.

Chief instructor Billy Billingham will also return with his team of directing staff Foxy (Jason Fox), Rudy Reyes and Chris Oliver, while they will be joined by former Special Forces psychologist Dr Alia Bojilova.

The show will see contestants exposed to constant cold and wet as they undertake an array of SAS training exercises.

Speaking of the new series, Billingham said: 'As our course progresses, the standards expected will never faulter.

'From the very first second, the recruits will be expected to give 100%.

'Anyone not doing so will be gone before they have time to make their excuses. Our time is invaluable - we will not waste it on anyone not worthy.'

Series six of Celebrity SAS: Who Dares Wins will air on Channel 4 every Sunday and Monday from September 22, at 9pm.