Ross Kemp struggled to breathe whilst staying overnight at HMP Belmarsh.
Ross Kemp
The 55-year-old actor was locked inside one of the country's most notorious prisons for 'Welcome to HMP Belmarsh with Ross Kemp', and admitted he couldn't wait until he was freed from the cell so he could get some fresh air.
The former 'EastEnders' star - who is best known for his former role as Grant Mitchell on the BBC One soap - said: "It is about 33 degrees in this cell.
"I'm lucky, I have got a three-man cell to myself.
"You are dealing with a pecking order and the politics of three men breathing in each other's bad breath and smells when they go to the toilet.
"There's no air because there are no open doors."
Ross admitted you'd have to be "mentally tough to survive" such conditions.
He continued: "I'm struggling to sleep. There's a lot of conversations happening, people shouting. You have to be mentally tough to survive. I'd be a liar if I wasn't relieved to be getting out."
In the first episode of the two-part ITV documentary, the documentary maker met some of the 4,000 inmates, who can only have visitors by "appointment only".
He said: "All new prisoners are brought into the first-night centre.
"Each prisoner is allocated a cell and contact with the outside is now by appointment only."
Ross first met with Tyrone Brooks - who is spending his second stretch in the jail - who gave the star an insight into prison life.
Tyrone said: "It's ruthless, it's vicious with all gangs. They have got problems which follow them from the outside world."
Ross also met with the only transgender prisoner, Claire Darbyshire, who was jailed for life for murdering her father but received a minimum term of four years.
She said: "At first, I found [it] very daunting. It was like, 'Oh my God I'm the odd one out here. How are they going to treat me as a trans person?'"
The second half of 'Welcome To HMP Belmarsh With Ross Kemp' continues on ITV at 9pm.
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