Inmate in El Salvador's CECOT prison says he has no regret after killing 30 people

An inmate inside the world’s deadliest prison who claims to have killed 30 people says he feels 'no remorse' and would do it again if he were ever released.

El Salvador, formerly known as the 'murder capital of the world', is now home to the world's largest prison - the size of 32 soccer pitches.

The facility is ran by director Belarmino García, a no-nonsense prison chief who oversees a regime widely regarded as one of the harshest in the world.

The prison operates under a strict set of rules, and despite holding 40,000 of the country's most dangerous criminals, discipline is rarely broken.

Access to the prison is limited; however, Channel 5 were recently granted permission to film inside the building for a new documentary, titled Richard Madeley on Murder Row.

But how exactly does García keep 40,000 deadly criminals in check?

Well, he sends inmates to be locked in a concrete hole with zero light for up to 30 days, if they even dare to think about breaking the extreme rules.

Inmates sleep on multi-layer metal beds. (Alex Peña/Getty Images)

Presenter Madeley was able to interview one of the prisoners, known as 'psycho', who claims to have murdered 30 people in El Salvador.

The inmate said: "Maybe we cry at night, but in truth, there is no change in us.

"All of us know that one day, even if this did stop we will return to do the same things outside."

And 'Psycho' is just one of tens of thousands of inmates who will never be released from the walls of CECOT, with many serving sentences over 700 years.

While critics of the prison have called it a breach of human rights regulations, the facility appears to be popular in El Salvador.

The inmate, known as 'psycho' claims to have killed 30 people. (Channel 5)

Director García has defended the way it operates, including a 24/7 lighting system, which means cells are never in darkness.

"It's simply part of the protocol, I need to be able to see what they are doing," he added.

The only item allowed inside the cells is a Bible - beyond that, inmates are not allowed screens, books, or newspapers, and talking must be kept to a minimum.

And when Madeley asked García if he considers the conditions 'cruel', he simply responded that they are 'necessary to be in control'.

The prisoners are counted daily despite rigorous security, and are kept in the cells for 23 and a half hours of the day.

Richard Madeley on Murder Row is now available to stream on Channel 5.