This mini-series, helmed by critically-rated writer-director Joe Ahearne was shown on Channel 4 in 1998 and set an unusually high standard for a British horror-fantasy-thriller. As my terminology suggests, Ultraviolet is one of those genre-spanning jobs, and - having just watched it again after a good few years - seems all the better for it.

The plot is of a fairly familiar type. Honest London cop Mike Coleman (Jack Davenport) is at his best friend's stag night when he receives a call from an informer who claims his life is in danger. Mike reluctantly decides to help, but the informer is already dead by the time he finds him. The assailant - who has gunned his victim down in a busy amusement arcade - disappears. This is strange, as the killer apparently went into a Tube station, but doesn't appear on any CCTV footage.

Stranger still are events the following day, when Mike's friend Jack doesn't turn up to his wedding, putting a bit of a crimp in the day of the bride, Kirsty. Mike, the best man, is somewhat conflicted as he is carrying a torch for her. This will have consequences later on... Then a mysterious investigative unit takes over the case, and Mike finds himself investigating them, as they are not regular police.

By the end of episode one it's clear that Jack has become a vampire, though the term is never used in the series. Instead the special unit refers to them as Code Fives, from the Roman numeral V. Geddit? The vampire-hunters are government-funded and equipped with interesting gizmos to tackle the undead. For instance, because vampires can't produce an image of any kind, they are not only invisible in mirrors but also can't be photographed. So the hunters have video cameras fixed to their guns, which fire special carbon bullets to provide a more effective 'stake' in the heart.

Ultraviolet, which ran to only six episodes, is refreshingly strong on both plotting and characterisation. Each of the vampire killers has his or her reason to fight the 'leeches', as they're dubbed. Thus Dr Angie March (Susannah Harker) was forced to kill her husband and one of her children because they were 'taken'. Ex-soldier Vaughan Rice (Idris Elba) saw his comrades taken in the first Gulf War. And the head of the special unit, Pearce Harman (Philip Quast), is a former(?) priest for whom the existence of supernatural evil seems to confirm the existence of God.

For their part, the vampires have a more interesting agenda than the usual freelance bitey/lurkey stuff. Indeed, as the series develops it becomes clear that a number of projects undertaken by the vamps are all part of a very dark and grand design. Some of the best plot twists relate to questions of how vampires might handle the pesky human habit of reproducing, getting awful diseases, and wrecking the ecosystem. Vampires, after all, have to take a very long view.

Sometimes the series is a bit too clever for its own good. The vampire not casting an image thing is smartly handled at first, and it makes sense that they also can't be heard on the phone (so they must use voice synthesiers). But then we're told you can't even take their fingerprints because that's an 'image' too. So does this mean I can't see a vampire because I wear glasses? Lenses form an image after all.

Such minor quibbles aside, though, Ultraviolet is one of the best UK horror-fantasy series of all time. If you enjoy clever stories and a rather grimly realistic approach to the vampire question, you might give it a try.