Last night's viewing - A Mother's Son, ITV1; The Treasures of Ancient Rome, BBC4

Watching a certain kind of television thriller, I sometimes wonder whether I'm communicative enough in day-to-day conversation. Take A Mother's Son, for example, which was only a few minutes in before a classic example of the kind of helpful fact-sharing I have in mind. "It's been nearly two years now," a teenage boy said to his divorced mother, obviously anxious that she might have forgotten how long it was since she'd left his father. A few minutes later her new partner was in on the act too: "We knew it wasn't going to be without its difficulties," he said, about a little family spat. "I mean, what are we? Two months in?" "Seven weeks and three days," she replied, clearly a woman who likes a degree of precision when it comes to redundantly exchanged information.

Anyway, we know where we are now, which is the point. A recently blended family with a lot of step-sibling rivalry, and thus the perfect setting for a tale of divided loyalties. A young girl has been found dead in a nearby reed bed and Rosie (Hermione Norris) is beginning to fret about the bloody trainers she's found under her son's bed. Far more significantly, she found the washing machine on when she came home putting his uniform through the heavy-stain cycle, a fact that I would have thought was the next best thing to a confession. I've occasionally threatened to kill my teenagers to try and get them to put a load of washing in and that didn't work. But I think they might think about it to escape a murder charge.

If you're wondering why she doesn't just ask him how he got blood on his trainers, and why he'd lied about losing them, the same thought occurs to her new partner. "Oh, for Christ's sake, David!" she replied. "He's already vulnerable after the divorce." Well, quite. You wouldn't want to upset him with a relatively straightforward enquiry, would you? Makes much more sense to set yourself up as CSI Southwold, buying hydrogen peroxide to test that ominous stain, bribing the local computer nerd to access his browser history, and secretly enlisting your ex-partner to follow him around town. What drives a thriller like this – which sets up an intractable tension between maternal love and growing suspicion – is the question: "What would you do?" But they tend to work better if you can minimise the number of times viewers look at the unfolding action and say, "I'd never bloody well do that".

"I'm setting out to debunk a myth," said Alastair Sooke at the beginning of The Treasures of Ancient Rome. Before he could do that, of course, he had to conjure one up, which was his contention that everybody thinks the Romans were just about gladiators and aqueducts. "To say that the Romans didn't do art is just nonsense," he told us indignantly. It is nonsense, but I'm not sure anyone worth listening to has ever said such a thing, and he didn't bother with chapter and verse so we could check.

Anyway, if you want a survey of some very fine pieces of Roman art, interspersed with shots of Sooke tootling around Rome in a Cinquecento, this should suit you down to the ground, provided you're not too allergic to worked-up aesthetic responses. "It's so harrowing to look at," said Sooke, looking at a first-century bust. "It's terrifying." Was he terrified and harrowed? I just didn't believe it, I'm afraid, any more than I believed him when he said he was "overwhelmed" by the sheer volume of art in Pompeii. You studied at the Courtauld, Alastair. You knew what was there before you went, which is why it figured on the shooting schedule. Time to sit down in front of The Shock of the New – still fresh after 30 years – and learn some lessons about how words go with pictures.