Most programmes on ERB are presented and produced by prisoners
At Electric Radio Brixton they're used to jokes about a captive audience.
But the prison radio station is no laughing matter. The station has won two Sony Radio Awards - the Oscars of the radio industry - including an audience participation award.
As I queued up to hand in my mobile phone, I reflected that the prison puts most radio stations' security into perspective.
I'd had my instructions - no laptops or other electronic equipment apart from my recorder and microphone.
And there were several more locked gates before I was shown into the education room and broadcasting studio that form the heart of the prison radio station.
Electric Radio Brixton (ERB), whose tag line is "making waves behind bars", is run by the Prison Radio Association (PRA), an award-winning educational charity which supports prison radio as a way of trying to rehabilitate offenders, and help reduce re-offending.
It is largely funded by grant-giving foundations and is now working with the Ministry of Justice to develop a national prison radio service.
The project has the full backing of Paul McDowell, governor of Brixton prison
The charity's chief executive, Phil Maguire, is a former producer on Radio 2's Jeremy Vine Show. He says prison radio can act as a "bulletin board" for the prison, providing information, educational content and advice for its listeners.
"If prisoners are nearing the end of their sentence, the station can prepare them for release, advising how to re-establish or maintain the relationship with the family, how to find accommodation, further training or employment, and how to address issues they may have while they're in here such a bullying or drug misuse," he says.
"All of these are issues which have been identified as key to reducing re-offending."
Other prisoners get a more hands-on benefit, learning how to be radio producers and presenters. Mr Maguire insists they're not training DJs or encouraging prisoners to expect a career in the media. It's more about instilling discipline and a work ethic and encouraging confidence and creativity, he says.
The PRA runs six-week production courses at Brixton in partnership with Kensington & Chelsea College.
You do something that the officers don't normally do, you let prisoners know what is going on as it happens
Ashley, prisoner at Brixton
I met Nash, a young prisoner who'd just completed the course and produced two programmes, one on re-offending, the other on religion in prison. I asked him what he thought he'd got out of it.
"I know within myself I can do certain things which I never really pushed myself to do when I was outside" he said.
"It's given me a lot of self-confidence and belief. It's re-opened my ideas and my ambitions, so it's done a lot for me."
ERB broadcasts for 24 hours a day, mainly music but with a significant amount of speech, focussed on what the outside world would call Drivetime.
The station was set up in Brixton 18 months ago by the PRA as a flagship project to show what could be achieved, with the full backing of the prison governor, Paul McDowell.
He'd seen the potential of prison radio at Feltham Young Offenders Institution, where the UK's first prison radio project was set up 15 years ago.
ERB's station manager, Andrew Wilkie, has worked at BBC Radios 1 and 2, 5 Live, World Service and Gcap Media, and presents some programmes himself - particularly those where an independent chairman is needed for discussion topics.
But most programmes are presented and produced by prisoners.
That includes an interview with former Cabinet minister - and prisoner - Jonathan Aitken, which won ERB one of its four Sony nominations.
Prisoners can take six-week courses in radio production
The interviewer, Tis, is halfway through a four-year sentence and memorably asks Aitken: "You chose to swim in shark-infested waters. Looking back now, would you get involved in the arms industry again?"
Aitken says no, but insists that "in fairness, a lot of things that were said about me being an arms dealer were untrue".
He describes his first night in prison and how frightened he was after hearing lurid and obscene threats shouted about him by other prisoners.
The Aitken interview has only been heard so far by those inside Brixton (the broadcasts cannot be heard outside the prison walls) but as a result of the Sony nomination it is likely to get a wider airing.
ERB's mission and programme content all sound very worthy but do prisoners actually listen?
Wilkie and Maguire took me onto A Wing to find out. We spoke to several prisoners at random and quite a few said they did listen and clearly knew the schedule.
There are plans to have more radio stations in prisons around the country
Then, as I interviewed Wilkie, he received a totally unprompted endorsement from Ashley, a prisoner who said he recognised the station manager's voice - from the radio.
"It's brilliant, the information that you hand out," he told him.
"You do something that the officers don't normally do, you let prisoners know what is going on as it happens. You are literally the voice that the prison officers cannot be - keep up the good work."
The ringing tribute could have seemed too good to be true - but I can vouch that it was not prompted or pre-arranged.
Not everyone is so pleased. The station managers and prison governor are well aware that some critics - not least in the media - feel prison should be tougher.
But they believe radio really can help reduce re-offending - and they see the Sony nominations as an important endorsement, as they work with the Ministry of Justice to launch a national prison radio service.
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