If you caught the first couple of episodes of the weekly late-night 15-minute comedy series Strangers on Trains (Wednesdays, Radio 4, 11pm) you might have dismissed it as Alan Bennettishly genteel and gone back to bottling sloes (which is what the Platonic Radio 4 Listener in my head is eternally occupied in doing). Well, not so fast. The series has shed its stage-fright and is going places.
Writer-performer Nat Segnit appears as himself, interviewing random men on trains across the country - characters all played by the actor Stewart Wright, strutting a peacock's fan of accents and tones. At first we had a Welsh postie inventing letters to the neglected wife of a (possibly dead) squaddie in Afghanistan - undemanding stuff. But then the show, which until now, like a swimmer entering the North Sea, had rather dilatorily minced up to the scrotum-line, took the plunge into deeper waters.
So a man from Northern Ireland described how, since converting to an unspecified religion, he'd been occupied with making a film every day of himself sitting in silent prayer trying to not move. "How often do you do this?" asked Segnit, moderately freaked out. "I've done it every day for the 27 months since Tina left me." The man's aim, it turned out, was to construct a time-lapse film of the next 30 years of his life without his wife - a film that he could show to her if and when they were ever reunited. At its best the writing is a little Chris Morris-y: bleak vignettes unfurl according to an inexorable, unstoppably ramifying comedy logic. And each episode is topped and tailed by Segnit's ruminations on that week's major themes - an exquisitely light parody of the "thoughtful" Radio 4 presenter's musing manner.
"Home," Segnit breathed in one episode, with an audible middle-distance gaze, "Home-coming. Home-sickness . . ." He was interrupted by an announcement over the tannoy that someone had just killed themselves under the train. A rail employee said that on trains you can detect the sound of death all the time if you know what to listen for. "You can hear the small mammals go like clockwork. It's like someone saying 'pssst' except backwards, like, 'tsssp'." Segnit started to worry that he might have recorded the soft crunch of the recent suicide on his dictaphone. Like Werner Herzog in the documentary Grizzly Man hearing a recording of the film's hero being eaten alive by a bear, he wasn't sure whether to enshrine the tape or chuck it out of the window and split. This could have gone on almost indefinitely, you felt, like a good riff from the late novelist David Foster Wallace, a plate that wouldn't stop spinning.
"The vanishing point of the tracks . . ." Segnit mused last week. "That point that seems like an ending. And thus a beginning. But is neither." He has the voice down definitively, the voice that makes you wonder whether all Radio 4 features must be produced on a drug called "Damp Sensitivity", which makes the user begin his every sentence, "And yet, sometimes it seems . . ."
The series ends on 1 October, with a teenage boy using an erotic Georgia O'Keeffe flower painting as a masturbatory aid, tragically unaware that it is in fact (long, but beautifully logical, story) a portrait of his own estranged mother's genitals. More, please.
Pick of the week
The First War on Terror
28 September, 9.30pm, Radio 3
Hari Kunzru investigates Britain's first "war on terror" - against anarchist bombers in the 1900s.
A German Hero
29 September, 8pm, Radio 4
A debate about the new film Valkyrie, in which Tom Cruise plays Hitler's would-be assassin.