Together, back home in our piano room, we worked through the Bach sonatas and partitas, the concertos and sonatas of Mozart, Beethoven, Mendelssohn, Bruch and Brahms, the chamber music of the early moderns. While he practised scales and arpeggiated runs, I mugged up the teaching manuals of Leopold Auer, Josef Joachim and Flesch himself. It may sound perverse, but in pre-television times clever boys often amused themselves by devouring dense books. My political reading served me well as I devoured the great violin ‘methods’ and summarised their contents. At nine and ten years old, we brought to our mission the obsessiveness that children apply to building sandcastles and model-train sets. Doing it together redoubled our competitive dedication. Some mornings we set our alarm clocks for six to get in two hours of music before breakfast.

Dovidl’s determination was fierce and his self-tuition was assisted by my readiness to plink out rough accompaniments on the piano any time he asked. Before my amazed ears, he invented and perfected his time-stopping rubato – which, if memory does not mislead, he adapted from a practical tip by Auer, Heifetz’s teacher. With me as personal listener, he picked up speed and mastery without shedding grace and wit. There was no doubt in my mind that he was destined for greatness.

By the end of that first severe winter, Dr Steiner declared him ready for a public début. ‘I have such joy from the Kinder,’ he told my father, who confided afterwards that Steiner’s daughter and grandchildren had been unable to leave Germany in time. ‘Not only from the artist Kind , but from der andere as well.’ He beamed, indicating me. Dr Steiner had been refusing to accept the envelopes that I thrust on him with payment, which is why I had called Father in.

‘Dr Steiner, I cannot let you teach them for nothing,’ he objected.

‘Is nichts for nothing,’ said Steiner. ‘They are my future.’

A solution had to be improvised. Mrs Steiner was deteriorating fast and Mother arranged for the couple to be housed, at our expense, in a refugees’ nursing home in Belsize Park, a Spartan, bare-floorboarded establishment, but one that offered more care, comfort and human company than the leaky Carlton Hill garret. Each Wednesday, after our session with Dr Steiner, Dovidl gave an impromptu ten-minute recital in the residents’ lounge to cries of ‘Herrlich! ’ and ‘Wunderschön! ’

A return visit to Albert Sammons reinforced Steiner’s endorsement.

‘He’s ready, y’know,’ said Sammons. ‘I’d give him the Elgar, Simmonds, and put him in front of an orchestra tomorrow.’

But Mortimer Simmonds performed at his own tempo. ‘Not yet,’ he told the mentors, ‘there’s plenty of time. He must grow some more, physically and emotionally. In his father’s absence, I have a paternal responsibility towards him.’