OCS, the elite squad which is at the centre of Touching Evil (ITV) is not so much a police unit as a well-armed therapy group. Every now and then the members break off from pursuing serial killers to catch up on a spot of mutual psychiatric assistance. "He needs you to come through for him" one will whisper urgently to a colleague; "Get over it," another will snap, after momentarily losing patience with the long process of healing. Notionally, at least, this general lowering of the spirits has been brought on by forced intimacy with human wickedness; "It's the job, Dave," DI Taylor said consolingly to her boss, after he'd made some melancholy confession of inadequacy. But any half-way competent doctor could see there's no great mystery to the malaise which afflicts every member of the team. They're suffering from Seasonal Affective Disorder, brought on by the criminally low light levels in which they work. Their offices combine a subterranean gloom with an icy blue raking sidelight - as if they'd set up their headquarters in a snow-plugged cave. And while there is the odd desk light around, it is an unbreakable rule that it illuminates only what is placed exactly beneath it.

Viewers who have suspected the existence of a covert and shadowy team working alongside OCS - a crack group of lighting designers, who secure all locations before the arrival of the detectives and transform them into dismal theatres of cruelty - were given conclusive proof in last night's programme, which included two scenes set in a discarded swimming pool (discarded buildings are a drug for the show, incidentally, but an economic drug for all that - last week the St Pancras Hotel provided sets for the killer's flat, the murder site and a Romanian hospital, all in a single episode).

In the first of these scenes the maniac was washed in a chilly daylight which illuminated every bleak, municipal tile. But by the time the boys in blue had arrived they needed torches - every skylight and window had been expertly blacked out apart from a gable oriel which let in a narrow, angled column of illumination. This was being chopped into fragments by one of those big ventilator fans, an indispensable style note for the modern serial killer. All this could have been the maniac's work - we had already seen the impressive son et lumiere of war footage which he had constructed in his hideout - but the scale of the job indicated a professional team.

Understandably everyone was fantastically gloomy by the end, having failed to prevent several more murders, but it's difficult to take their distress seriously when you know it could all be put right with four or five sunlamps and some tungsten uplighters. If I'm not mistaken the Director of Photography's name is David Ooo, which seems somehow appropriate.

They would like that name on Wogan's Web - a new daily daytime programme on BBC1 which further extends the franchise of the Lad from Limerick (I'm sorry about that alliteration but the tone of bantering frivolity is contagious, and that's just about the height of it).

This is essentially zoo-television for the Saga set - an unfair remark because Chris Evans wouldn't be doing the things he is doing without Wogan's radio example. Unfair or not, on television these devices - a noisily appreciative crew, on-screen producer figure, a simmering mutual wind- up between all those taking part - look as if they come in a direct line of descent from The Big Breakfast and TFI Friday.

There are guest spots, which allow Wogan to try his hand at such activities as barbershop harmony and tai-chi, but a good deal of the programme consists of him reading out jokey faxes from the already devoted viewers - viewers with names like Hugh Rinal and Mick Sturbs. Wogan is just the right man for the job - as relaxed as if transmission is already over and he's sinking a few in the green room - but if you're wondering how he keeps up the unceasing flow of talk listen closely for recycling. "Keep it down to a dull roar there," he said to his telephonists yesterday, a line which last appeared during Saturday night's Eurovision presentation, while a nice phrase about the sun "splitting the paving stones" made it in for the second successive day.