Astonishing to Dyer was how many times a face could change in an hour. It animated Rougetel to recall his months in the north, the hours he spent crouched over the ice, searching for a seal’s hidden breathing hole. He half-rose out of his chair, his face filled with glee. His right hand was the sled he had pushed across the frozen sea, his left was the moving wave he had watched petrify into a scroll, and the uneaten rice cake was a whirling wall of snow in which his feet stood invisible. By the glow of a seal-oil lamp inside his fetid igloo, he worked his way, page by page, through a dictionary spotted with fat – the white steel rod – in which, recognising the condition to which he aspired, he had underlined the Netsilik word for polar bear, tara-i-tua-luk = he who is without shadow.

From the clean white crucible of Nunavut, his true features emerged. He reflected: ‘To be adult at such a young age, it splits you open.’ After fourteen months, he was ready to strike out on his own, make sense of the world for himself.

In the spring the ice melted. He left the snow and the seals, headed south. Summer found him in Cochin studying the Upanishads. To his Spanish and his smatterings of Aymara and Inuktitut, he now added Sanskrit. The research suited him. He discovered that he loved it. Languages led to linguistics, linguistics to artificial intelligence. The more he read, the more he hungered to read. ‘I wanted to know everything.’

The effort he might have dedicated to a thesis, had he stayed on at Cambridge, he ploughed into his life’s project: a careful study and sustained meditation on the meaning of the texts to which intuition, curiosity or blind chance would lead him.

His practice was to take one subject at a time and master it. He sought out the acknowledged authorities, read their works with stubborn interest, clarified his thoughts. He devoted his next winter to the Theosophists; the winter after that to the rise and fall of the Nabateans. Since then, he had immersed himself in – counted on his crushed fingers – philosophy, history, science, biology, mathematics, economics, medicine, psychology, astronomy, anatomy, archaeology, politics, physiology. Seeking the interconnectedness that lay in everything, he meandered from subject to subject, one fertilising another, to investigate how it fitted into the universal puzzle.

He swallowed his rice cake in quick gulps. He was grinning now. For the first time, he was telling someone who had known him, who might possibly understand, the extent of his journey.

To cram nearly forty years into a conversation over lunch is not easy. Dyer’s sense of Rougetel’s life was riddled with gaps. What did he do for money, sex? Had he been in love? What did he regret? Most of all, was he ill, on drugs?

These were questions Dyer kept to himself. He hoped they didn’t show on his face.