I enlisted the help of the Israeli poetaster attaché, who responded warmly and energetically. But neither the Tel Aviv immigration service nor the police had seen anyone answering Dovidl’s description, dashing my hopes that he had sought a Jewish homeland.

I wrote to my father’s ministerial contact in Warsaw and got no answer. I wrote again, with the same result. Much later I learned that the poor man had been whisked off and killed in a Stalinist purge against ‘rootless cosmopolitans’, meaning Jews.

I applied for a visa to visit Poland, but was turned down. I did my best to keep the story alive in the press, praying for a sighting, but newspapers are not renowned for their constancy. A new story had excited their attention: the sinister disappearance to Moscow of a pair of high-placed British diplomats, Guy Burgess and Donald Maclean. ‘Does your story have a political dimension?’ I was asked by a news editor.

After three months, the inspector called to say he was closing the file. Mother was spending more time in a nursing-home than out, and Father was staring blankly at his towering pile of correspondence. I was finally free to mourn, in the few months until Father died.

I made one last concerted effort to pick up Dovidl’s trace shortly after Father’s death, when I became head of the family. Through one of those seedy fellow travellers who thronged the fringes of concert life and contributed occasional reviews to the Morning Star, I made contact with a person in authority at the Polish embassy – not the ambassador, but an intelligence officer listed as the junior commercial attaché. The Poles were starved of hard currency. I needed cheap scores. I ordered from them two hundred thousand paperbacks at sixpence apiece, a total of five thousand pounds, which I paid from a pre-war Swiss account that my father had discreetly set up.

This was the riskiest thing I have ever done. British citizens were forbidden at the time to spend more than fifty pounds abroad without Treasury consent; their foreign accounts were supposed to be held under Treasury supervision. If discovered, I would have faced prosecution and a prison sentence of up to three years. Like every illegal act, it exposed me to the possibility of blackmail. My Polish contact knew that I was evading currency controls: he could betray me to the British authorities or pressure me to perform other services for the Poles. I knew the depth of my exposure and took steps to contain it. I slipped the Polish attaché a thousand-pound sweetener, which did the trick.