I suppose I have a vague picture in my mind of a sort of idealised solver, who is a combination of everybody I've loved. 'It seems to work that way, yes.' And does he feel he knows them? 'It's hard to say. Your solvers feel they know you, I say, because they have spent much of the last half-century puzzling out your character. Partly this is because his default expression is a smile that lights up his face, but mostly it is because of his engaged, amused intelligence. Graham, who set his first puzzle for the Guardian 55 years ago, seems younger than his 91 years. Inside, it is ordered and cosy, calm and quiet except for two clocks ticking a hurried, insistent counterpoint. Flat, frost-rimed fields stretch for miles around. The Reverend John Galbraith Graham – aka Araucaria, the Latin name for the monkey puzzle tree – has for the past 18 years lived in a tiny cottage in the village of Somersham, Cambridgeshire. I imagine the person being just the same.'

Araucaria's puzzles … are fair, honest, complex and have a deft wit. I've never seen crosswords as a challenge: they're a unique way of engaging with another person's mind. 'Your vocabulary, intelligence, wit and imagination being teased and excited by the setter. 'It's not a solo pursuit, it's an intimate exercise,' said brighton2k. 'No other setter comes near to attaining his fusion of knowledge, originality, humour and consistency,' said another. It is a 'brain-joy' doing his puzzles, wrote one. Some admitted to completing their crosswords through tears others devoted their comments to trying to explain why Araucaria has meant so much to them over the years. The reaction online is extraordinarily heartfelt and moving. 'The rubric sends your eye down to that clue, you run through the six-letter signs of the zodiac, and before even writing it in, your stomach has lurched.' A colleague, who did the crossword with her daughter, said: 'It was like watching a photograph slowly appearing out of developing fluid.' And her daughter turned to her in shock, and said: 'I think this must mean he's dying of cancer.' 'For me, there was chutzpah in making that 18 Down easy for regular solvers,' wrote a puzzle reviewer, a few days later. Just over a week ago, thousands of people turned to the Guardian cryptic crossword, saw it was by Araucaria, and settled in for a quiet hour of pleasurable frustration, but soon found themselves assailed by a growing sense of foreboding.

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