The week on radio
"The past is difficult," stated the protagonist of The House of Doctor Dee (Radio 4, Monday) at one point. A trite remark, not especially well put, but at least it's unarguable. The past is the one foreign country we can never hope to visit; we must construct our picture of it using unreliable and often contradictory information, mostly gleaned from guidebooks written by people who have never been there - or, at best, have a confused recollection of its fringes.

Oddly, though, and also a little annoyingly, The House of Doctor Dee was constructed around the opposite view: here, time is an illusion, the centuries reach out to one another, and the past turns out to be about as difficult as a trip down to the newsagent's - just as in a number of Peter Ackroyd's other yarns. This is mostly, I suppose, because he has some firm convictions about the circularity of time and the possibility of an ongoing relationship with the past. But, at times, it does feel as if what drives his fiction is not so much conviction as convention, when he seems to be stuck inside a genre just as firmly as Barbara Cartland or Agatha Christie. It's just that his genre - the time-bending, mystical, London novel - is a little more unusual.

In this case, the plot revolves around a house in Clerkenwell that was once the property of the Elizabethan magus John Dee, and in our own time has passed to young Matthew Palmer. As the story progresses, it emerges that Matthew is a foundling, and that his late father believed him to be a magical homunculus created by Dee and fated to die and be reborn every 30 years. Over the centuries, the homunculus has been instrumental in, among other things, nurturing the careers of Isaac Newton and Charles Babbage, as well as working on radar during the Second World War. Meanwhile, back in the past, Dr Dee discovers his friend and fellow magician, Kelly, to be a fraud and a traitor. Matthew concludes he is not a homunculus; and he and Dee speak to one another across time, declaring the hope that, through "vision and imagination", they can dissolve the illusion of the reality of time, and London will become "the mystical city universal".

A nakedly silly story, in Alan Drury's dramatisation veiled with wisps of meaning. If Claire Grove's production had punctured the pomposity, offered some faint sense of irony, it would have been easier to respect it; as it was, she took it all with a very straight face, which probably made it more enjoyable. In fact, it was huge fun; but for all the wrong reasons.

Still, even when Ackroyd plays fast and loose with time and history, he writes with the understanding that they are problematic. The Cuban Crisis (Radio 2, Tuesday) - marking the 35th anniversary of the US blockade of Cuba - was one of those frustrating programmes which seems to think that a sense of period can be faked up with a bit of old newsreel, vox pops and a couple of hit records. The narrative was streamlined enough, but a recital of events was insufficient to conjure up the atmosphere of apocalyptic paranoia that the script seemed to aim for. A wider view might have helped; as it was, the listener was left with a sense of impending nuclear catastrophe as something quaint and provincial that our parents experienced in the early Sixties.

A profounder understanding of the difficulties of untangling the past lay behind What Are They Looking At? (Radio 3, Sunday). Piers Plowright's feature, one of his last before he retires from the BBC, was gentle, thoughtful and playful - an examination of the many things that Jan Van Eyck's The Arnolfini Marriage might mean. The picture's many ambiguities (most famously: is she pregnant?) were presented from the point of view of experts and members of the public, with interpolations from the painter himself.

The tone was perpetually questioning, even good-naturedly badgering, until the very end when, disappointingly, it settled on an answer: that what the picture shows, unambiguously, is the traces of its own making, both the circumstances in which it was painted and the character of the artist. An answer that's no answer; it would have been better to leave the question hanging.