Meeting Cleo’s warning eyes, I placed the sugar cube on my tongue and let it rest there in a small show of defiance. As the children flung back the front door and rushed towards the gate I hesitated for a last moment. When Cleo had gone, slamming the door after her, I swallowed a mouthful of water.

“Right,” Dick told me. “You’ll feel something in about half an hour, so sit back and relax. We can play chess.”

“I’ll look at the garden.” I could usually beat Dick at chess, but this was one game he would enjoy losing, as the pieces turned into dragons. I listened to the children’s shouts fading down the street, followed by Cleo’s strong, cheerful voice. Herself a single parent, she had implied that I was stepping out of character, a responsible father taking this questionable drug, still legally available in England, though there had been frequent calls to have it scheduled.

I stared at the toy-cluttered garden, a moraine of happy memories that the past three years had deposited on this suburban plot. The glacier had moved on, Miriam sleeping calmly within its deeps. The children had almost forgotten their mother, something I had tried to prevent, mistakenly. If they remembered her it was on other levels, in their good humour, resilience, and confidence in unearned affection.

Strangely, Miriam had begun to recede even from me, while at the same time standing out more clearly in my memory. She seemed like the statue of a madonna suspended above the nave of a cathedral, rising into the air as I stepped away from her. The perspective lines of my life still led back to Miriam, but I owed a great deal to the women I had known since her death, above all to Sally Mumford, who had helped me to face head-on the pressures of pain and obsessive sexuality. Curiously, Sally’s open infidelities had helped to ease my memories of Miriam, as if her death had been an infidelity of a special kind.

However, Dick had not been keen on having Sally present when he offered to supervise my LSD experiment. Her sudden swerves of mood, her muddled enthusiasms, might derail the hallucinatory locomotive. Eager to make the experiment and explore the locked doors of consciousness, I agreed that Cleo Churchill should look after the children. The amphetamines and drinamyls I had sometimes taken seemed less mind-altering than the average double Scotch, but Dick assured me that LSD was pushing against the limits of the brain.

I remembered his presentation to the head of the BBC’s science programmes, as he outlined the projected series in which I would take part. Confident as always that he held his audience’s attention, he had prowled around his display charts of brain sections and ECG readings like a pitchman selling the human brain to a party of intrigued visitors from another planet.