Rob Brydon has lifted the lid on a peculiar rule imposed on the contestants of his new BBC gameshow, Destination X.
The ten-part series sees 13 strangers compete for a £100,000 prize and the chance to embark on an adventure of a lifetime.
In a unique road trip, they are whisked around Europe in a large coach, clueless about their location or destination as they strive to decipher the truth from the clues, deceit, and lies they're presented with.
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With sensory deprivation onboard the bus and no contact with the outside world, the contestants are challenged to deduce their possible location after being given a series of clues and red herrings.
They're gradually eliminated until the winner is left standing, based on their guesses of their locations at the end of each day, with the person predicting the furthest away from their actual location being booted from the game, reports Wales Online.
Hosted by Gavin and Stacey actor Rob, who accompanies the players around the continent, Destination X has been dubbed a hybrid of The Traitors and Race Across The World.
But unlike The Traitors, which was filmed in a plush Scottish castle, and more akin to the conditions contestants face on Race Across the World, Destination X contestants had to endure living on a bus during the month-long filming.
This meant sharing a single toilet, prompting Rob and executive producer Dan Adamson to disclose certain rules that were implemented.
Before the series went to air, Rob confirmed to journalists that he wasn't bunking down on the bus alongside the contestants, choosing a rather more comfortable arrangement instead.
Dan then revealed: "You plan and you plan and you plan and we had the most amazing production management team, and you plan everything, you think of everything, but we set ourselves a rule which gave ourselves one problem, which was that there was no number twos on the bus, and that was the rule.
"It's a worldwide rule, right? And then suddenly it was like, 'Why do these people need to go to the toilet so often?'
"So we had to create a system, which was that we had a convoy behind the bus, we had a special car with a trailer that had a couple of porta-loos on it.

"So we had to find places to pull over, and goggles had to go on, producers would chaperone them off, take them to the door of the porta-loo, get them in, goggles off, do your business, wash your hands, put your goggles back on, and back in the bus. It was stuff like that."
In an effort to maintain the secrecy of the bus and contestants' whereabouts, they were forced to implement additional measures.
"Even giving them food, everything had to be decanted out of any local containers, we couldn't give them food that felt specific to the country," Dan revealed.
Speaking about the enormous scale of the high-budget programme, which was filmed across 32 days and required 190 crew members who needed 7,000 hotel rooms in 30 different hotels as they travelled 11,000 km throughout Europe with more than 40 vehicles, Rob revealed it was unlike anything he'd experienced previously.
He hinted: "I love the thought of the scale of it, because I've never done anything in television with that scale. We go all over Europe to some fantastic places, so the appeal was working on a show of that scale."
"We had the chance to turn Europe into a board game, so we immediately thought that the way we bring scale to the challenges is we just get incredible locations and we take over whole castles, we run a train on a public network, we take over cable car systems, the scale just goes up and up and it's like, actually, what fun can we have with those toys?" the producer Dan added.
Destination X airs from 9pm on BBC One and iPlayer tonight.
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