‘It’s somewhere over there,’ I say vaguely, pointing beyond the great neon-lit mountain range of department stores, restaurants, cafes, noodle joints, love hotels and all the epic activity of central Tokyo.

Marlo rolls his myopic eyes, bleary with jet lag behind his specs, and although he doesn’t actually tut, he comes quite close.

‘Somewhere over there, right, Mum,’ he says, unimpressed, and now he has his phone in one hand, his thumb tapping a frantic blur, his guidebook in the other, and a see-through umbrella balanced on one bony shoulder.

I leave him alone to concentrate and look at the city I have not seen for ten years. The lights of TV screens ten storeys high flare and blur and melt in the driving rain as we stand at the crossroads of the world, my beautiful boy and I, trying to find a bar, one bar, a special bar, out of all the thousands of bars in Tokyo.

Then suddenly there is the unmistakable tremor of an earthquake.

I feel it rattle through me – that old, almost-forgotten feeling of a train passing right in front of your face – and then after a few long seconds it has passed.

Marlo looks up at me with concern.

‘Just an earthquake,’ I said. ‘Happens all the time. It’s nothing. It’s not the big one.’

The earthquake is already over and the crowds at the Shibuya crossroads have not even paused. The great tectonic plates deep below the earth have shuddered but are now still.

Marlo closes his book, puts away his phone and adjusts his see-through umbrella. His first earthquake has shaken him and for a moment I recognise the look on his face. It was the look he used to get entering a soft play area when there were bigger boys casually bouncing up and down.

He pushes his glasses up the bridge of his nose and gets a grip.

‘Dad’s waiting,’ he tells me.

My father did his time but he did not die in prison.

The cancer inside him, the tiny part of his body that was betraying him, could not kill him. The policy of watchful waiting had worked out well. But Dr Khan, who had urged my father to go for surgery, was not so fortunate and died from a stroke at just forty-nine.

‘Bloody tragic,’ my father said.

He had been a model prisoner. Always good with his hands, the prison workshop was his natural habitat, and younger men who had no clue what to do with their hands apart from take another selfie flocked to him to learn about metal work, and dovetail joints, and taking apart the engine of a car and putting it back together. After a few years, he was encouraged to take a Certificate in Counselling and Mentoring (duration 200 hours, Level 4 Prisoner’s Education Trust). My dad liked to boast that it was the first qualification he had earned since the certificate for swimming his width at school more than fifty years ago. I imagined him helping lost young men to find themselves, but he said it wasn’t really like that. Mostly, he taught them to read and write. But that was no small thing, my dad said.