A strange and grizzly opening to the new series of Horizon saw Michael Portillo examining both methods of execution down the ages, and his own personal position on the death penalty. Indeed that’s where we start, with Michael admitting that he had initially voted in favour of state executions. Then he’d worked out that we could never be certain we were killing the right person, and voted against on his second chance. I don’t know what was more surprising. That he’d taken so long to realise the obvious, or that a politician had reached the right conclusion in the end.

With his obligatory nod to his previous life at the heart of political cut and thrust out of the way, we were off on a roller-coaster journey through all the ways the human race has traditionally meted out the ultimate sanction, after which we were taken on a magical mystery tour looking for the ultimate in humane killing. A contradiction in terms, surely, as the most humane way to do it would be: not to do it.

Hanging. There’s more to it than meets the neck. The old American way (known as “short drop” because…err…there was a short drop involved) was not very successful. There are cases on record of convicts being “hung” three times and surviving. Now that’s got to smart. The Brits, naturally, being more efficient, decided the success rate would increase if the drop increased. So we invented “long drop” (I’ll leave you to work out the difference). This was a lot more successful but came with the unfortunate side-effect of occasionally decapitating the victim. Unfortunate for the cleaners, I mean.

Talking of decapitation, I found it strange that there was no mention of the guillotine in last night’s programme. Perhaps the most famous and notorious execution method of all time was totally absent from Portillo’s consideration. Possibly because it’s no longer in use anywhere in the world, I guess, and so didn’t count in the struggle to find something more humane.

The next sickening experiment was to show how the electric chair could fail. They used a pig – fortunately dead already – since it’s the closest thing to a human they could find. No comment. As I mentioned before, viewers of the Green Mile will already be aware of the importance of achieving a good connection with the victim’s head by using a real sponge soaked in brine. In the absence of this connection the electricity doesn’t flow properly and the unfortunate criminal cooks instead of dying. And, if he’s lucky, then dies. I told you this was grizzly. In the Green Mile the wayward warder doesn’t soak the sponge. In last night’s experiment, we were shown the effect of a warder who saved money by buying a synthetic sponge. The pig’s head basically melted. I was glad I’d had my tea several hours before.

Even lethal injection, which until last night I’d thought the most humane method, was shown to be potentially extremely painful in the wrong hands. And it’s always in the wrong hands because doctors aren’t permitted to perform executions. I’d assumed a heavy narcotic was always administered, but sometimes it’s not, and sometimes it’s not given long enough to work. Executions by injection have been suspended in many states of the US while the Supreme Court decides whether it is a “cruel and unusual” form of punishment.

We were then treated to an interview with a redneck who demanded to know why prisoners should be allowed to die in peace and tranquillity when their victims hadn’t enjoyed such a privilege. In his view, execution should be as painful as possible. Clearly the message he’d picked up from his Bible-bashing had been more “an eye for an eye” rather than “two wrongs don’t make a right” but don’t get me started on the interpretation of religious tomes.

Our man Portillo set off to find a better alternative. Clearly he, or the programme makers, believed an alternative was required. I suppose with 55 countries using the death penalty the chances of a “nil” alternative being accepted are slim, so the next best thing is to find that painless method.

Gas (cyanide) isn’t painless, apparently. It binds to the same place as oxygen in the body’s respiratory system, so you effectively suffocate even though you keep breathing.

More esoteric methods were examined. Things known to be dangerous in excess – like G-force. Wasn’t this just an excuse to show some of the whizz-bang science that Horizon is known for? No programme is complete without at least one centrifuge – the bigger the better. The ones used for pilot training are some of the biggest of all, so here goes Michael – accelerated up to 9g to the point of unconsciousness. “I’m going grey,” he cried out feebly. I could have told you that Michael without you going anywhere near a centrifuge.

But that’s not a nice experience either, so strike that off the list.

It turns out a state of deathly euphoria can be introduced by breathing nitrogen. So all we need to kill people is a cylinder, a hosepipe and a mask. Glad we got that sorted out.

Next week: the effects of total sensory deprivation. I think the producers have developed an unhealthy obsession with torture.