Television is taking an interest in prisons: Prison Break, Criminal Justice, Louis Theroux in San Quentin. Virgin TV is even planning a series in which public figures (its PR doesn't like the word “celebrities”) spend time behind bars. It sounds exploitative. I am assured it isn't. But it will have to go some way to be as worthy as Banged Up, which contained no laughs at all and left you feeling good just for having watched it.

This four-part reality show/social experiment is presided over, Alan Sugar-style, by the tortured figure of David Blunkett, a Torquemada of a Home Secretary now repenting of failing to be fit for purpose at his enforced leisure. Banged Up fast-forwards the boring old business of waiting for troublesome young people to receive their first custodial sentence by taking ten as yet unjailed troublemakers and persuading them to spend ten days somewhere that looks like and is run like a jail but actually hasn't been a jail for 100 years.

Blunkett said it provided a second chance for these miscreants, an opportunity to thwart their destiny as jailbirds. But it was also, he added disarmingly, a second chance for him, for as Home Secretary he had failed to invest enough in such experiments. I understand that what actually turns out to work for these boys is not the short sharp shock of their incarceration but the “restorative justice” and group therapy work they do in their ten days inside, that and the lectures they receive from the reformed old lags who, much to their surprise, join them in the old Scarborough Prison.

The first episode, however, showed how effective a short sharp shock can be. The secret is that although it must seem an eternity at the time, ten days is not long enough to get used to anything. Two of the youths could not handle prison even for a night. Jamie Owen, known to the Sunderland police for theft, shoplifting and fighting, rang home. “What's it like, like?” said his father Nigel, who had gone to jail for manslaughter when he was 19. “F***ing 'orrible,” his son summarised. A few hours later he was going bonkers and the prison shrink was called in. “Prison,” said the governor, David Wilson, dismissing him, “is not for you.”

It is easy to blame parents such as Nigel for their sons, but Tom Davis's dad, Derek, a technician, seemed all right. Tom, he admitted, was the sort of lad he would cross the road to avoid. He showed us some coasters his son had given him for his birthday. They were themed. One said “Drunk”, another “Pissed”, a third “Squiffy”. Tom had found them funny and also a bargain at £1. But Tom's own drinking was not a laughing matter. After one night off the bottle, his detox was going so badly that he too bailed out, on medical grounds. He's 17.

If this is not easy reality television to watch, it is even harder to listen to. Its stars are less articulate than the average Big Brother contestant and hard to make any sense of at all. It made me think that if schools gave themselves only one priority it should be to teach children self-expression. But the boys are still interesting cases.

I am on the case of one of them in particular, James Tootell, a charmer whose mother once went to market only to see her own favourite ring on sale there thanks to her thieving son. James stole crisps from the prison kitchen and spent a morning vandalising his cell. We left him about to see the prison guv'nor. He said he couldn't wait. I can't either. I want him broken. By looking at the underlying causes, this programme, you see, shows how Home Secretaries like Blunkett are made.

Back in fantasy crime land, New Tricks turned up for its fifth series, complete with Dennis Waterman's terrible theme song and the worst performance of Alun Armstrong's career. (Amanda Redman and James Bolam in contrast are very good.)

Last night's opening episode was so full of back story that this irregular viewer could hardly follow it. I appreciated, however, the professionalism of its writers, Roy Mitchell and Douglas Watkinson. They came up with some decent jokes. The plot involved donar transplants: cornea, heart, liver, kidney. “Sounds like a recipe from the River Cottage,” said Waterman. That made me laugh. And, because the show is only an hour, scenes are short and the plotting is taught - unlike almost every other British crime drama you could name. A short sharp indulgence for the older viewer.

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