A television preview for The Tablet

It is 1753, and London has just acquired its first professional police force, the Bow Street Runners. The force is the creation of the novelist Henry Fielding and his brother John, both of whom are magistrates. In City Of Vice (Channel Four, January 14th), a five-part historical drama series, we follow them as they learn to investigate crimes, starting with a series of grisly attacks on prostitutes.

Fact and fiction are artfully intertwined. Central to the plot is Jack Harris, the most notorious pimp of 18th century London, and his infamous List Of Covent Garden Ladies, which listed 400 prostitutes, with details of their ages, looks, and specialities. When girls start being mutilated and murdered in the "bagnios" and bathhouses, Harris comes under suspicion, especially when the brothers find a correlation between the timing of the attacks and the women being deleted from the list.

We seem to have seen a lot of 18th century squalor and decadence on television recently, but this is well done. Georgian London looks right, and writer Peter Harness has managed to come up with a plausible — and often extremely coarse — idiom for his characters to speak. "Man is an animal of passions, sir," says Harris, when chided for the brutality of his trade, "and pretty much all his dealings have some measure of cruelty."

Henry (Ian McDiarmid) and blind John (Iain Glen) make an unlikely crime-fighting duo, despite John's near-superhuman powers: he is said to be able to identify 3,000 criminals by voice alone. They start with high hopes — an acquaintance is convinced they'll end London crime within five years — but have to learn the art of detection from scratch. Idealistic and pious, they have, nonetheless, the appetites and attitudes of most men of their era. John, particularly, nearly comes undone — in all senses of the word — while interrogating one of his female informants.

The result is a police procedural in a historical setting. There's even a scene of the detectives sticking pins in a huge map on the wall, as seen in hundreds of cop-shop dramas. This one won't satisfy fans of serious crime-writing — the unravelling of the central crime is feeble — but the 18th-century low-life setting has been well researched and gives the series an interest it would otherwise lack.

At one point the Fieldings threaten a witness by reminding him that there are 233 capital crimes on the statute book. Capital punishment is still a grisly reality in 55 countries around the world, with the USA the most prominent. But judicial killing is a lot more problematical than it was in the days of the Fieldings, not only ethically but practically: we know — and care — a lot more about what happens to people at the point of execution, and it is not pleasant. In The Science Of Killing, an extraordinarily distasteful Horizon programme, Michael Portillo is sent to investigate not whether capital punishment should be carried out, but how. "He wants to find a method that is, unquestionably, humane," says the voice-over.

Now that Horizon has succumbed to the disease of celebrity-led television, it is not enough for the former cabinet minister to wander round asking questions of experts on the subject, although he does a bit of that. Instead he has to undergo various ordeals "that will take him to the brink of death". All this is slightly more dignified than eating bush tucker in the Australian rain-forest, but only slightly, and in the context of judicial killing borders on the obscene.

Portillo's views on the death penalty are only touched upon in passing. It seems he voted for it in the 1980s, then changed his mind in the 1990s, after noticing that there were a lot of miscarriages of justice. For the purpose of this film, he does not offer a view. Instead he adopts a pragmatic approach: societies will continue to execute people, he thinks, so the task is to find the most humane method of execution.

Every method currently in use is examined and found to be lacking. So, in consultation with experts on animal killing, Portillo comes up with a new system for painless execution, involving a poison gas that has the side-effect of rendering its victims euphoric at the point of death. Then he sets off to sell the idea to an American enthusiast for the capital punishment. At which point, it became apparent that Portillo has been rather naive: a painless death is the last thing the death penalty lobby want.