The Week in Radio: Art historian Janina Ramirez proved that a painting can come to life on air even if you can't see it

Some subjects inevitably fall flat on radio. Nature can be a struggle – if the critter in question can't croak or coo engagingly into a microphone then, really, who cares? Cooking is far worse. It should be one of the Ten Commandments for broadcasters everywhere: Thou Shalt Not Fry, Bake or Chargrill On Air. Seriously, Woman's Hour, I love what you do, but unless you are prepared to courier one of those "perfect tapas" dishes directly to my doorstep then I don't want to know.

Visual art can be tricky, too. On the face of it, discussions of Renaissance masters would seem perfect for the Radio 4 demographic. But how does the presenter render vivid paintings to an audience who are effectively blindfolded?

This week the art historian Janina Ramirez circumvented this problem at the start of Melencolia by suggesting that we Google a picture of Albrecht Dürer's engraving of the same name. In doing so she was acknowledging that if we couldn't see the work, her documentary would be a waste of all our time. I liked her style.

So I did as instructed and found myself face to face with a pissed-off angel who looked like she had just got to the front of the Ryanair queue to be told that her wings counted as carry-on luggage.

There was nothing especially pretty about Dürer's masterwork, which is now 500 years old, but its contents remain a riddle. Images of the engraving famously adorned the homes of Sigmund Freud and Einstein. The composer Harrison Birtwistle, one of the programme's contributors, based a piece on it in 1976.

So what exactly had ruined the angel's day? What of the similarly sour-faced cherub to her left? And what was the significance of the dog, all skinny and hunched, and the utensils, the key and the unopened book?

The presenter went to the British Museum to see two original prints of Melencolia, so she could properly drink in the texture of ink on paper, though it didn't help her join the dots. She talked to Patrick Doorly, author of The Truth About Art, who had a theory about Plato that sounded pretty convincing, but he couldn't know for sure.

Would these questions ever be answered definitively? Well, no, as that would ruin 500 years of art historical sleuthing. But by mulling over the possibilities and encouraging us to really study the painting, Ramirez managed to bring the puzzle of Dürer's sad angel to life. As Birtwistle told her: "The whole idea of mystery is more interesting if we never know what it means."

Mystery isn't something you'd associate with Laurence Llewelyn-Bowen, one-time king of the domestic make-over show, though one should concede that he knows a thing or two about colour, which is presumably why he landed that most coveted prize: The Programme With The Presenter's Name In The Title.

Radio 4's two-parter Laurence Llewelyn-Bowen's Primary Colours began in front of the cobalt blue cockerel on the fourth plinth in Trafalgar Square, before transporting us to Venice, the one-time hub of European colour that handled spices, textiles and dyes from the East, and engaging in a deeper discussion about "the most expensive colour on Earth", ultramarine.

Llewelyn-Bowen had gathered a heavyweight assortment of historians and experts whose research helped to illuminate the history and politics of colour. This was just as well as there was precious little gravitas in the presenter's own delivery as he rolled out vowel sounds like a bingo caller.

Llewelyn-Bowen may know his stuff but matters would be improved if he didn't address his listeners as if they were morons.

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