Philip Roth: always unsmiling. Photograph: Douglas Healey/AP

Having interviewed plenty of novelists, and found some of them scary, I think I could sympathise with Mark Lawson as he conducted his "exclusive" interview with Philip Roth for Radio 4's Front Row. Conducted in the New York office of Roth's agent, it certainly felt as if the novelist was in charge. The great man had been dragged out of his rural fastness, but had ditched his famous prickliness and was all the more daunting for being thoroughly good-humoured. In photographs Roth is always unsmiling, gaunt, staring down the photographer with a hint of anger. In the interview we heard him mellow-voiced, often amused, occasionally laughing. For the interviewer, it was most unsettling.

He even got playful. Lawson was inviting Roth to muse on the title of his new novel and found himself put on the spot. "Exit Ghost" is a stage direction found in three of Shakespeare's plays, observed the novelist. "Hamlet ... ," he began. "Macbeth," Lawson added, a little too keenly. "Can you name the third one?" quizzed Roth. There was a palpable pause, before the interviewer was put out of his embarrassment. "It's Julius Caesar". Lawson, the most literary and well-read of interviewers, seemed stumped by the information.

At another telling moment, Lawson pointed out that the makers of the film of The Human Stain had been unable to replicate the role of Nathan Zuckerman as the narrator of the novel. The difficulties faced by the hapless adaptors clearly tickled Roth greatly. "That's not the only problem they had making The Human Stain," he replied, his chuckle dissolving into guffaws. What was he thinking of? The Viagra-fuelled sex? The angry mockery of political correctness? Lawson was too unnerved by the sound of Roth's laughter to find out more.

Roth, as one would expect, pooh-poohed the supposed similarities between himself and Zuckerman that Lawson kept asking him about. Yet, with the interviewer well under control, he was finally happy to accept the association when it was convenient. In the new novel, Zuckerman, as the years run down, is cramming in the novels of the 19th century, and his creator told us that this did indeed reflect how he had been spending his time. "I have begun to re-read the great writers that I haven't read since graduate school." A literary author's final assertion of authority: the confession that he really needed to do some re-reading.