"WE love nothing more than to declare other people insane," Jon Ronson told an attentive audience of psychopath-seekers.

Despite dedicating months of his life to tracking down psychopaths, the best-selling author cut a humble figure on stage clad in a professorial patchwork of pale browns. About a third of the crowd thought they knew a psychopath. Whether they left any the wiser is open to debate.

But what they did get was an enhancement to his 2011 book The Psychopath Test, with a couple of guests telling fascinating stories. Ronson touched on his encounter with Scientologists (he “got in there before Louis Theroux”) and elaborated on meeting a man at Broadmoor who said he faked insanity to avoid a jail term.

The author also recalled visiting the ruthless 1990s corporate asset-stripper Al Dunlap at his mansion filled with monuments to predatory animals to see if the man really was a psychopath. One of Ronson's guests, Mary Turner Thomson, neatly summarised psychopaths: “They're the predators, we're the prey,” she reflected, having married a man who claimed to be in the secret service and ended up fathering children with multiple partners.

Ronson's other guest, former student Eleanor Longden, gave a moving account of hearing voices in her head one day at university and then living a torturous ten years facing her demons. While the night plotted similar territory to Ronson's book, what it missed was the methodology behind his investigation.

He did, however, reveal a weakness: realising when he had disregarded fragments of his interviewees' lives that didn't fit into a psychopath tick-box. Another amusing yet poignant section focused on the porn industry, though its relevance to the evening wasn’t clear.

A closing Q & A gave people a chance to probe further. Most revealing, perhaps, was finding out Ronson is not as taken with spotting psychopaths as he was when he set out on his odyssey of insanity.