Horizon: How Violent Are You? (BBC2, 9pm)

YOU can nearly hear TV viewers cheering at the sight of a politician being beaten around the head by an assailant in a fight.

It makes a change from Newsnight’s Jeremy Paxman giving them a tongue-lashing.

That’ll teach them, I can imagine you’re thinking, to fiddle their parliamentary expenses.

The scene in Horizon, however, is not a constituent getting retribution for creative accounting but one-time politician Michael Portillo in his new role of Horizon reporter.

He describes himself as a calm and peaceful person. “I’ve never been in a fight in my life. I don’t have a single aggressive bone in my body,” he tells us at the start of the programme.

The documentary wonders what would make him an angry young (well, middle-aged) man, one who could be driven to violence or commit a dreadful crime, such as murder.

He throws himself into the task fearlessly as he discovers what it’s like to hit someone or be pushed to breaking point by lack of sleep, meets a man who has taken a life, and witnesses members of the public asked to torture fellow human beings.

First stop is the Bolivian Andes, where violence is celebrated as a way of keeping the peace. Violence, as he puts it, is on the curriculum.

The cameras prove it as fighters slug it out in bloody punch-ups.

The rules are simple: Only fight someone the same age and size. Knuckledusters and gloves covered in metal chains are allowed. This is tinku and this sort of fighting is a part of life, a means of settling both personal and family disputes.

Portillo is put to the test. This pacifist, who’s never hit anyone in his life, is pitted against a competitor. After a few minutes of sparring he takes time out to comment, “very violent, very tiring, I don’t like it”.

He changes his tune as the fisticuffs continues. He fights back and knocks his opponent to the ground. So much for the man of peace. Portillo admits he’s “very surprised – I knocked him down but it was quite nice”.

Experiments form part of the programme, the most worrying of which is a repeat of the Milgram study which asks: Would someone give a stranger a lethal electric shock in the name of science?

The answer is yes. Nine out of 12 go all the way and press the switch delivering a 450 volt shock, despite the screams coming from the recipient in another room.

Just remember – don’t try that at home. Or the one in which Portillo participates.

He’s deprived of sleep for 36 hours by having to look after two screaming babies that don’t allow him more than a few minutes shut-eye at a time.

The babies aren’t real, but Portillo’s increasing exasperation is. Tests show his aggression levels rise as the hours pass.

It helps him understand what lies behind crimes of passion and why anyone would shake a baby. “Any one of us could crack,” he suggests.

And he admits what makes him mad – IT rage, which is like road rage only it happens in the office. Portillo owns up to attacking a computer with his fist.

And two fax machines and an alarm clock. I hope he doesn’t respond the same way to bad reviews of his programmes.