Consider this first.
The series described itself as the most elaborate hoax perpetrated in television history.Source: Wikipedia
A group of twelve contestants (who answered an advert looking for "thrill seekers") were selected to become the first British televised space tourists, including going to Russia to train as cosmonauts at the "Space Tourist Agency of Russia" (STAR) military base, with the series culminating in a group of four embarking on a five-day space mission in low Earth orbit. The show and space mission contained aspects of Reality TV, including hidden cameras, soundproofed 'video diary' rooms and group dormitories.
However, the show was in fact an elaborate practical joke, described by Commissioning Editor Angela Jain as "Candid Camera live in space" and claimed by Channel 4 to have cost roughly five million pounds. Unknown to the "space cadets", they were not in Russia at all, but at Bentwaters Parks (formerly RAF Bentwaters, a USAF airfield from 1951 to 1993) in Suffolk staffed by costumed actors, and the "space trip" was entirely fake, complete with a wooden "shuttle" and actor "pilots". In addition, three of the Cadets were also actors, included to misdirect any suspicious Cadets and to help reinforce the illusion.
Channel 4 had contingency plans if the contestants realised the hoax; Johnny Vaughan repeatedly suggested they would have to play old rerun episodes of Jamie's School Dinners, and after the "launch" some unchosen Cadets would have been used as a backup crew.