Former Tory minister Michael Portillo pushes himself to the brink of death investigating humane methods of executing criminals for Tuesday night’s Horizon.

How to Kill a Human Being screens at 9pm on BBC2 and examines the crisis in capital punishment.

In Vietnam shaky marksmen have brought into serious question the reliability of the firing squads. In Iraq Saddam’s half brother was hanged and decapitated by mistake. And in the United States the use of lethal injection has ground to a halt as the Supreme Court examines whether prisoners are actually dying in unnecessary pain.

Portillo looks to science to provide a better solution and in so doing, he experiments with hypoxia – the lack of oxygen to the brain – which is gaining support as more humane means of exeuction.

VIDEO: click here to watch Michael Portillo’s experiment