‘Is Dovid – David you say in English – and Eli,’ he responded with a grin. ‘But my family says Dovidl for short. You call me Dovidl.’

Discommoded by his unEnglish familiarity, I replied stiffly: ‘My name is Martin L. Simmonds. L for Lewis.’

‘Mottinl?’ he laughed. ‘I call you Mottl.’

Introductions over, he demanded to know my age. Well-read as I was, he seemed somehow older and wiser; in fact, he was three months my junior, nine and a quarter to be precise.

‘Are you musician?’ was his next question.

‘I play the piano a bit,’ I conceded.

‘Me, I am violinist – prodigy. I come to study with Professor Flesch. You know Flesch?’ I had heard of him; I realised what was going on. The lad was a boy-wonder, victim of a trade I had heard my father condemn as child slavery. Simmonds, he pledged, would never present a soloist who was too young to buy a drink. Remember that, Martin, when you take over the firm. Yes, Father, I said, wondering how old you had to be to buy a drink.

‘Professor Flesch says I am genius,’ the boy continued. Well, fancy that. Father was going to be thrilled to be disturbed by a would-be child slave and his pushy parent. He could be frosty when roused: the pair might find themselves escorted smartly to the front door before Florrie could bring us that ice-cream, drat it.

‘Do you play chess?’ the boy asked, running his long fingers over my ivory set. ‘Come, I beat you.’

And so he did, two games in less than twenty moves each, the thrashings sweetened by Florrie’s strawberry ice and by the boy’s, to me, mystifying refusal to gloat over crushing victories. ‘You are solid player,’ he said clinically, ‘you need good tactic. Me, I am genius, I play brilliant. You, not so genius, must be patient, wait for weakness, go in where other person is blind.’

I was staggered by his analysis. This boy-wonder had, in two brutal games, assessed my qualities, outlined my options and advised me how to maximise my potential. ‘I’ll beat you at draughts,’ I offered.

‘Of course, no problem,’ said Dovidl. ‘Draughts is small game, small possibilities. You play white with correct formula, you win. But chess is big, not possible to make formula. You win, you are like God; you make order out of chaos.’ He pronounced the word khu-yess. ‘Is like music. You play good, the notes form structure, make sense. Is good ice-cream.’

Between spoonfuls, his eyes darted round my room like searchlights. He had yet to utter a superfluous word, let alone a definite or indefinite article. He must have had a vocabulary of a hundred useful nouns and verbs, but he used each word like a naked sword, unsheathed of social nicety.

Running his fingers along my shelves, he took down a recent Left Book Club pamphlet on the Danzig Corridor. ‘What news?’ he asked.