How is an episode of Celebrity Big Brother made?

Here's everything we bet you never knew about what it takes to make Celebrity Big Brother:

1. Making Celebrity Big Brother is a military operation

There are 67 cameras recording all of the action that goes on inside the Celebrity Big Brother house 24 hours a day, seven days a week.

“Everybody has an opinion of the content that’s on screen,” explains presenter Emma Willis. “But I think what they probably don’t think about so much is how that content actually got on screen.

"There are people writing down every single word that is said 24/7,” she adds. “And then there’s the people that decide which parts of 24 hours make one hour of television.”

Bafflingly, there’s a team of 36 people who are just dedicated to conceiving and executing the tasks.

Series editor Steve Earley adds: “The main challenge is getting the show on the telly every night at 9 o’clock.

“It’s a huge, huge production. There’s no script, there’s no running order, there’s no rehearsal. We have to take what happens in the house today and put it on the show tomorrow night.”

2. The whole house is controlled by the producers

Just like in Jurassic Park, there's a main light board that shows with red and green bulbs just which doors in the CBB house are currently locked and unlocked. For example, this means that the housemates can be contained in an area like the kitchen if the producers need to enter the garden to set up a task.

"We have control of the house," explains series editor Steve Earley, who describes the celebrities as if they're dangerous velociraptors. "There’s lots of doors that lock and unlock and it’s important that the housemates don’t have control over the doors locking for example.

"We have to keep the housemates contained and we have to keep them safe. So what we have in the gallery is a massive big lightbox where we can lock and unlock doors whenever we like."

3. Although things can – and do – go wrong

As former housemate and Bit on the Side presenter Rylan Clark-Neal explains: "Electrics can go wrong and wrong doors can unlock by mistake.

"I remember when one day I was in the house we had a gym and I saw that the eye was green above the door and I thought ‘they only open the gym for an hour a day’ and I pushed the door open and there was a lovely cameraman standing there that I started talking to and he got really frightened and just wouldn’t speak.

"And then Big Brother had a go at me to shut the door and I had a go at Big Brother and said ‘well you shouldn’t have unlocked the door should you?’ Happens all the time!"

4. There’s a maze of ‘camera runs’ around the house

Behind the one-way glass in the CBB house is a labyrinth of blacked-out walkways called camera runs. These do what they say on the tin and literally allow the camera men and women to move around the perimeter of the house undetected. Well, almost.

"As a housemate that’s all you hear sometimes – wires being dragged about by noisy cameramen," explains Rylan, who says that every day he goes up to the camera runs for "a little walk around" to nosy on the housemates.

He also showed us the not-so-secret-secret-staircase. When John Barnes left the house via a backdoor eviction, he walked into the Diary Room from one end and then left out of the other.

As Rylan showed us, John would've walked down a staircase, out of the door with 'Diary Room' written on it and then he was released into the camera runs.

5. There’s a storyboard

Celebrity Big Brother might not be a scripted drama, but there are people behind the scenes constantly working on stories and plots for the series. In fact, there’s a whole cabin just dedicated to crafting the narrative that unfolds on CBB.

"Once the story producers think they have a story, they commission it and it goes up on the story board and that commission goes to the edit," says series editor Steve Earley. From the picture you can see such stories include ‘Task wake up / task reveal’, breakfast with rations and Malika in the Diary Room saying she wants to leave and 'Malika confides in Ginuwine’.

Steve explains that generally they’ll have 25 stories a day that go up on the board and 14 of those go into the final cut. “It’s really important that our story producers all day are constantly looking for stories, constantly looking to develop our threads throughout the day and make sure those commissions are going through to the edit for the stitch overnight," he says.

6. Tonight’s show has already been made by 9:30am today

The first rough cut version of tonight’s show has already been finished a full twelve hours before its transmitted.

After the last of the housemates go to bed – which can be around 3am to 4am – the team work throughout the night editing the stories together in order to get the first main cut of the show ready for its initial viewing, with people including the executive producers and Channel 5's lawyers at 9:30am.

"The really exciting thing about that morning viewing is that sometimes it may go down very well, sometimes it won’t go down very well," explains series editor Steve Earley. "And that’s the really tense bit.”

Taking on board any notes on the episode, edits are then made.

7. Marcus Bentley’s office is, um, basic

You would have thought that being employed on the same show for 18 years would get you a pretty nifty and posh office from which to work from. But... no.

Narrator Marcus Bentley (above... and yes, that's what he looks like!) in fact spends his working day inside a minuscule blacked-out building that looks suspiciously like a shipping crate that's been sliced in two. Don't believe us? This is it:

Told you.

Anyway, the script is worked on and finished at around 2pm ready for Marcus to lend his dulcet tones to it.

He explains that he's already watched the show (he's sent a link in the morning to view the episode) and they then have to deliver a really quick turnaround. Sometimes very quick.

Marcus says he’s previously done Big Brother shows where something so dramatic has happened that while part one of the show was being broadcast, he was still recording the voiceover for part four!

"It’s a very organic, immediate process filming, recording and editing this show," he explains. That's one way of putting it.

If all goes to plan the voiceover is done, the show is sent to Channel 5 at around 7pm and it's ready to be broadcast at 9pm. Then the next day, the whole thing starts all over again...

Celebrity Big Brother airs 9pm on Channel 5