AS ONE becomes older and grouchier, words or terms emerge that, by their mere appearance, induce apoplectic irritation and raised blood pressure. My list is headed by "spiritual", or "spirituality", but in the context of TV documentaries, snapping closely on their heels come "secrets" and "treasure". These are tabloid terms, employed to set the pulse racing.

Usually, the promised revelation turns out to be something that anyone with reasonable general knowledge has known for ages, or the fruits of new research which has, indeed, made a hitherto-unrecognised link - but labelling it as a "secret" poses the question: who intended it to remain hidden from the public gaze? "Treasure" usually turns out to be something interesting, but of little value to a Caribbean pirate.

Eager to learn all there is to know about our diocese's mother church, I couldn't miss Secrets of St Paul's Cathedral (Channel 5, Friday). A world-class team of structural engineers have been examining some of the world's greatest buildings with the aid of a state-of-the-art mobile laser-scanner. This, we were promised, would reveal new insights into how Wren created his masterpiece.

How does the stupendous dome stay up? The laser showed us how a brick cone supports the weight of the ball and cross; the outer dome is built as light and high as possible, and what we see from inside is a much lower dome. In other words, what visitors who climb beyond the Whispering Gallery can see with their own eyes.

Much was made of Wren's error in building on clay rather than on sand; no one had thought to check that the subsoil of London is, indeed, clay - there is no sand to build on.

The whole thing, generous and well-meaning as it was, appeared context-free, employing huge technological resources to discover things that every member of the fabric team already knew.

And Digging for Britain (BBC4, Tuesday of last week), the round-up of recent archaeological discoveries, has, despite its well-informed presenters, a distressingly high quotient of "treasures", replacing the cultural significance of this or that artefact with the (frequently untrue) implication that it must be worth barrowloads of money.

There was a great "cathedral" on display here, too - or, at least, the shadow of one. The significance of the Ness of Brodgar, in Orkney, is becoming more and more apparent: its complex of Neolithic monuments may have been more important than Stonehenge. Its great temple was some 82 feet by 65 feet, facing the chambered tomb of Maeshowe. Broken stone mace-heads point towards centuries of ritual activity, greatly extending the story of religion on these islands. Now that really is treasure.

UKIP: The first 100 days (Channel 4, Monday of last week), a dramatisation of what might happen if the party won the General Election outright, lacked profound political insight, focusing more on the personal challenges facing the party's supposed only black MP. In the end, she refused to toe UKIP's line, and wrecked her chance of high office. It was heart-warming - but its implausibility encouraged hideous nightmares of what might really happen.