You become quite mercenary if you spot a failing in yourself. Whereas most people would suppress or correct their flaws, I find myself thinking, ‘How can I use that?’ If something happens that leaves me looking like a chump, half of me goes ‘Grrrr’, but the other half is going, ‘Now, if that happened to Keith, I could take it a bit further.’”It sounds almost therapeutic – a means of transforming personal discomfort into art He pounces on the idea. “I used to be very wary of doing Keith in front of journalists, because they usually take that line of, ‘Oh, it’s just him, he’s the character,’ and I always found that a bit demeaning The implication is one of artlessness. But Keith is actually a combination of observation and what’s already there.

When you see a hand on the dashboard, that’s me.”In truth, I had intended to compliment his acting: he is nowhere near as close to Keith as I’d imagined he would be He seems placated. “Uncanny, isn’t it? Of course, a lot of the emotional scenes are done with a double I’m mostly used for the inserts. He gazes around the cramped tearoom with the kind of awe that most people reserve for the Grand Canyon “Mega!” he coos in perfect Keith-ese. “It’s like another world, isn’t it?”It’s disarming how that subtle facial adjustment transforms him instantly into Keith “Well, I look like him,” he deadpans.

My friends noticed that I had that look about me.” By way of explanation, his eyebrows levitate into his hairline while his mouth spreads into a baggy smile. Despite this, he can see the positive side in everything: his wife Marion’s affair, his estrangement from his “little smashers” – his sons Alun and Rhys – even the doubts cast over his younger son’s paternity in the second series, which saw the show’s 10-minute slivers upgraded to unbearably dark half-hours. It is likely that if Keith ever set eyes on a mushroom cloud, he would chirrup: “Well, yes, it’s the end of the world. But it’s something to tell your grandchildren, isn’t it?”"I was glad to get to the end of the last series,” sighs Brydon, “because I had taken on Keith’s persona. He addresses the audience exclusively from the driving seat, though that is the last position he could be said to occupy in his own life. “It’s not an easy watch.”The hippy mechanic in Alex Cox’s cult movie Repo Man observed that “the more you drive, the less intelligent you are,” and in Keith’s case you couldn’t argue that a life behind the wheel has not contributed to his mental erosion. A typical Marion and Geoff moment will show him addressing his in-car camcorder in his minicab, crowing cheerfully about some petty triumph or other, only to lapse suddenly into a despondent silence as he realises that he’s been sold a pup: for example, that the bank manager’s idea for clearing Keith’s £40 overdraft by foisting upon him a £3,000 loan was not so altruistic after all.”I can’t always see what people mean about the bleakness,” says Brydon, “but in the last series I did think, ‘Oh dear, we’re putting him through the mangle a bit.’” He sucks the air through his teeth.

Keith Barrett is the crumpled Cardiff divorcee in Marion and Geoff, the series of grimly comic monologues written by Brydon and Hugo Blick. Keith’s inability to read a situation verges on the autistic. I’ll trust you to decide.” After which the anecdote is scarcely worth the telling.”You should write, ‘He smiled’ after that,” he advises, following a delirious skit in which he has imagined a wild weekend spent “whoring” with Corbett. “Don’t put ‘shagging’,” he says, after using precisely that word.