CELEBRITY SAS: Who Dares Wins got off to a wobbly start with one star quitting just 32 minutes after arriving at base camp.
John Barrowman, famed for his role on Doctor Who and Torchwood, told cameras he joined the show in order to "prove himself".
However, after trying just one of the tasks, he voluntarily withdrew (VW) from the series less than an hour after arriving at base camp.
The star had only just been given his armband to mark the start of his journey, being marked as 'Number 13' after failing to impress in the first challenge.
But as the cast lined up to enter their bunks, Barrowman started to retch, and then immediately tore his armband off, threw it on the ground and walked away.
His fellow recruits and the DS staff were left in shock at the move, with staff Jason Fox asking, "Hang on, hang on, you've not called out. Are you VWing?"
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"Yeah I'm VW. I'm out!" he yelled back, before vomiting in a corner.
Billy Billingham went to check on the star, asking if he needed to see a doctor, but Barrowman refused.
"What do you mean you're done? You've only just got here, why?" Billy asked.
"I know. I just... I'm done," he responded, and when Billy pushed further Barrowman declared; "I said I'm out!"
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"I just... it's not for me," he added. "I know who I am. I know what I'm about, and it's not for me."
Back at base camp, DS Chris Oliver told the rest of the celebs: "Listen, stick together. Hate us as much as you want. Doing epic s*** like we've done today, you'll grow.
"You've just seen that sack of s*** out there, just handed these for band in and gone.
"You leave that gate when it's time for you to leave, and you'll be a better person. Trust us."
Fans of the show were left gobsmacked at Barrowman's quick withdrawal, and shared their frustrations about it on X.
Celebrity SAS Who Dares Wins winners
Many celebrities have attempted the infamous Channel 4 quasi military training course - but only a select few have successfully passed.
Series 1 (2019) - Wayne Bridge
Series 2 (2020) - Locksmith and Lauren Steadman
Series 3 (2021) - Alexandra Burke, Aled Davies and Wes Nelson
Series 4 (2022) - AJ Pritchard, Calum Best, Ferne McCann and Maisie Smith
Series 5 (2023) - Gareth Gates
"Strange decision from john barrowman," wrote one, while another declared him as "absolutely pathetic".
"Goes all the way to New Zealand. Quits in seconds. What the hell. Waste of money and time," said another.
"Even I might last longer than 32 minutes," said a third.
While a fourth said: "John Barrowman knows who he is. Guess we'll just have to guess"
In the time he was on the show, Barrowman said he was left "ruined" by allegations of misconduct made against him, including claims by former Doctor Who co-stars Noel Clarke and Camille Coduri he once 'put his penis on her shoulder while in the make-up trailer'.
The comment, which re-emerged during completely separate allegations against Clarke, resulted in the star being axed from Dancing On Ice, stalling his career.
On Celebrity SAS, Barrowman acknowledged that he had sometimes 'done stupid things' though refutes the claim it was sexually inappropriate, instead done as a prank.
"On Doctor Who and Torchwood, I had to do a lot of nude scenes," he told cameras.
"If I was being stupid, I would do something stupid, I would shake and waggle, or I might do a scene where I might have one of my b****** hanging out.
"The press made it out that I was a sexual deviant. We've all done stupid things and silly things, but what's been said about me will never go away now."
The military endurance series returned to Channel 4 tonight with 15 new famous faces acting as recruits for the course.
Heading to New Zealand, the group were quickly thrown in the deep end by being made to walk across two steel bars, suspended 300ft in the air over a ravine.
They were then put through a 'hostage rescue' scenario.
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Barrowman is currently the only member to withdraw from this year's series.
Celebrity SAS continues Monday at 9pm on Channel 4.