Exclusive – SAS: Who Dares Wins DS Billy reveals instructors have final say over producers when it comes to Channel 4 show

"It's a full teamwork, it's great teamwork. We've got our ideas and it's always good to have fresh blood, fresh ideas," he said. "So the producers may have an idea here about doing this off the mountain or how about doing this – but we'll look at it and go, 'Hang on – is it relevant to what we would possibly do in the SAS?'

"Not everything [on the show] we would do but there's a relevance to it – it might be to overcome fear, we might be able to overcome trust, which is a massive element in the SAS so it is relevant, but they'll come up with ideas like we do and then we'll look at it, we'll be sure it's not too dangerous, we don't want it to be too easy, and then we'll test it, look at it and then we'll go, 'Okay let's go with it.'

"So they do have ideas of stuff they want to do, but we'll be the deciding factor based on whether we can do it. And we do it – we go out and test everything. If there's an element of danger, we will test it."

On whether producers give suggestions when it comes to culling contestants off the course, Billy said: "They'll have a narrative, they'll have what they want, but no.

"It's full on. People sign up to it, they get on the crazy train that's going to move at a million miles an hour but that's the way it is."

He added that while producers may have seen more of the recruits behind-the-scenes, this means the instructors don't fall into the trap of favouritism.

"It's a clean sheet; everybody's come in for the same reason, everybody starts at the same point, only some will get to the finish line – it's as simple as that. That's life, that's the way it is and that's definitely how the selection works.

"We'll look at everybody from the second they arrive to where they get to, and if somebody's got the potential and maybe has a possible medical problem, we'll discuss that and go, 'Hang on a minute, is that worth another push? Give them another chance?' Then yes. If somebody is a complete liability and not got a medical issue, like we had with the first two, then that's different."

"So it's all assessed by us, not by the producers. Start, finish, reasons for and away we go and it's a great little system because there's four heads there, there's four heads deciding."

Sunday's episode saw the show's first transgender contestant Holly quit the course after struggling during the three kilometre climb.

SAS: Who Dares Wins continues on Sunday at 9pm on Channel 4. Visit our Entertainment hub for more news, or check out our TV Guide to find out what else is on.