Peter drains his tea and rearranges his gangly legs, tripping a passing waiter as he does so. He does not apologise. Peter is not the type to say, ‘Forgive me’. Self-obsessed, he feels only how things affect him, never the impact on others. He is about to betray his mother again.

‘Next morning I ring the doorbell and he comes running all flustered to the front door in his woolly dressing-gown. “Please don’t ring,” he whispers, “just knock. Ringing disturbs our day of rest. It activates an electric impulse and changes, however minutely, the serene state of God’s universe.”

‘Wow, I think. Everything he says has a reason, some kind of proof that he can find in one of those big books. “There is order in God’s world,” he told me once, “and it is our task to appreciate it. Just as there is a fixed order to the musical notes we play, so there is a heavenly plan governing all our actions, no matter how small. If I raise my hand to scratch my nose, that is because God arranged for me to do so five thousand seven hundred and forty-nine years ago at the moment of Creation. I am just an instrument that God plays at His will.”

‘ “But we learned in science that the world has been going for millions of years,” I say.

‘ “Not according to our calculations,” he insists.

‘Anyhow, that first Saturday morning, Mr Katzenberg takes me into this front room that seems absolutely poky because there’s a huge bookcase along one wall and a massive dining table in the middle. Bending down to light the fire, I spot a piano in the corner and think, Right first time – the man’s a musician. Then, on top of the piano, I see this terrific violin case, knocked about a bit but really classy. “D’you play?” I ask, pointing at the fiddle-case.

‘ “Sometimes,” he says.

‘ “Professionally?” I ask.

‘ “Once,” he says.

‘ “Can I hear you?”

‘He shakes his head.

‘ “Why not?”

‘ “Sabbath,” he says.

‘So the next day when I call for my money – fifty pence from him and an order to light Sabbath fires for his neighbours on either side – I ask to hear him play.

‘ “Are you a violinist?” he wants to know.

‘ “I’m going to be a famous soloist,” I tell him.

‘ “Come in.”

‘He opens the case and unwraps the violin from its silk scarf. I tell you, Mr Simmonds, I have never seen anything so gorgeous. Wood the colour of a bronzed medal and a sheen that seems to come from right inside. It’s a 1742 Guadagnini that the great Joachim used to own, you know, the man who inspired Brahms to write his concerto. It’s like something so holy you hardly dare look at it. I want to touch it, but I don’t even dare to ask. You can almost hear it breathe.