PICTURE Umberto Eco, vast of mind and body, dancing a tango alone on the sand, a walrus without his carpenter. No wonder Desert Island Discs (R4) has such enduring appeal, when it encourages such frivolous fantasies. Eco was stupendous, batting away Sue Lawley's polite enquiry as to the precise nature of semiotics by saying that if he could explain it in a few words he wouldn't have written all those tomes - he'd have sent a telegram. His choice of book was predictably unpredictable: he wants "an immense hypertext", viz the New York telephone directory, which contains every name in the world ...

Though probably not many Herods. To be thus christened was the unlucky fate of the Lutheran pastor ministering to the lost tribe of the Liawep. Edward Marriott met him, surrounded by armed warriors, just outside their settlement in a wildly remote and inhospitable part of Papua New Guinea. Herod's was an uphill struggle as, by preference, his flock worship Our Father the Mountain (R4). Marriott and his Catholic translator, Dunstan, found themselves pressed into attending Herod's service, which meant that the rest of the congregation chose, suspiciously, to stay away.

As if in terrible vindication, that night a thunderbolt killed a woman and four children. Marriott and Dunstan, by now clearly petrified, fled before dawn. Even the deadly Papuan black snake, even the jungle full of malarial mosquitoes was preferable to facing the headman of the furious tribe, despite his being dressed only in a pair of ladies' knickers.

This is the kind of programme for which radio was born: a lone reporter, whispering nervously into a microphone amid hissing jungle sounds, innocently pursuing a story that might kill him. And the tribe itself is threatened, not just by another fearsome missionary - this time a Seventh Day Adventist - but by a mining consortium planning to blow up the mighty mountain in their search for gold. Poor Marriott: a friend told him that people like him did more harm than anyone else when they explore such lonely spots, and he agonises. You can bet nobody said that to Dr Livingstone. Still, at the end, Herod's ragged choir could be heard singing a hymn to the tune of an old mining song, "Clementine". The music hung in the air, its clear implication being that the Liawep themselves will be lost and gone forever.

Robert Fisk is also troubled by his work. For Points of Departure (R4) he assembled recordings of recent battles we had nearly forgotten, one of which permanently damaged his hearing and left him with the maddening pain of tinnitus. It didn't, however, damage his vision, which is long and clear. Shells whiffling around him, he stood on the very paving-stone in Sarajevo from which Gavrilo Princip fired the shot that sent Fisk's father to war, suggesting bleakly that history is like a vast echo-chamber and that he can make little difference.

Yet he does: his insistence on finding out for himself, on not believing propaganda, is invaluable to his audience. In 1982 he interviewed an Israeli lieutenant who was happy for the world to know that he wanted to see every Palestinian dead - just a month later, a thousand of them were massacred in the Lebanese refugee camps. Fisk worries that he could have predicted it, but he could not have prevented it - and he witnessed it for us all. He has seen the whites of the eyes of evil, and his ability to fly, club class, out of mortal dangers which others cannot avoid is of little comfort to him. He feels more at ease in anarchy than in the order of a place like Switzerland, where crime means throwing a chocolate-wrapper out of a window.

On R3 Carey Harrison starred as the German portraitist Sir Godfrey Kneller in the last of Harrison's Bigwigs, his trilogy of plays about Purcell's contemporaries. Self Portrait with Dog became a hilarious duel between a pair of splendid hams. Jack Klaff as Rembrandt appeared to Kneller in a dream, roundly denouncing him for his perfunc- tory style. The accents grew thicker. "Vy" thundered the Old Dutch Master, "must you lenksen alvays ze ooval of ze faice? Eurrggh, Kaniller, you call vis bainting?" So the hapless Kneller tried painting his own portrait, with the help of the thundering instructions from his dead teacher, only to be howled down by the fashionable throng. Alas, he destroyed the picture: all that survived was the dog, who, with his warty, whiskery chops and sad ugly face, Kneller christened Rembrandt.

Finally, hooray hooray, I'm Sorry I Haven't a Clue (R4) is back, better than ever. I propose shamelessly to offer you pearls from this tiara of quiz shows whenever I can't resist them, starting with Willie Rushton's best. Given a well-known saying to complete, he suggested: don't get your knickers in a boot-sale. It's a tip the chief of the Liawep may need, quite soon.