Fearing that their lice-ridden clothes with the sewn-in lists might be stripped from them by so-called hygiene patrols, the Alte Rebbe ordered his Hassidim to memorise the names by reciting them at night after evening prayers. To stimulate the memory he invoked the methods of the Baal shem tov, Master of the Good Name, founder of the Hassidic movement. Gathering the simplest of Jews, the shepherd-boys and shleppers who never had a day’s education, the Baal shem (known by his initials as ‘the Besht’) proclaimed that literacy was not a prerequisite of piety. Sincerity was more precious in God’s eyes than scholarship. ‘If you cannot read the words in the prayer-book,’ he preached, ‘sing unto God a new song.’ And the Besht would vocalise a melody of his own, one tune after another, rapt and ecstatic in alternation as he turned dumb hearts to heaven.

The Medzhiner Rebbe, in graver circumstances, resorted to similar means. He composed a nigun to the names, solemn but catchy. As the list lengthened, he wove variations on his original theme. Then he added a contrapuntal extension, livelier and foot-tapping. A third melody grew out of that tune, then a fourth. Night after night, it was joined to evensong. On the choking cattle-truck to Treblinka, in the quarries and the barracks, the Alte Rebbe led his Hassidim nightly in sotto voce renditions of his deathless Song of Names.

‘What were the parents called?’ said the Young Rebbe softly.

‘My father was Zygmunt,’ said Dovidl, ‘my mother Esther.’ The Rebbe smiled, and shut his eyes. He began to hum, then to sing, tunefully in a low tenor voice. ‘Rapoport, ay Rapoport, ay Rapoport,’ he rhapsodised, patting the arm of his chair. ‘Vir hoben Rapoport, Avrum, Rapoport, Berel und Chayeh-Soroh, mit Kinder Yossl, Yechiel und Leah.’ The men and boys in the prayer-room chimed in, a ghostly chorus: ‘Rapoport, Chaim-Dovid, Rapoport, Shua-Chaim, Rapoport, Yerachmiel und Soro mit Yehiel, Shloime, Shneyur-Zalmen und Rivke, Rapoport, ay Rapoport, ay Rapoport, yehi zikhrom boruch, may their memories be blessed.’

Dovidl swayed with the melody, wondering if he should take out his fiddle and accompany. The Rebbe’s eyelids were unwrinkled, his face tranquil. On and on he sang, a capella, running through the Hebrew aleph-bet one Rapoport after another. It was not an uncommon name. Rapoport, Dovidl knew, was a conflation of Rav d’Oporto, a rabbi from Portugal, whence thousands of Jews fled the Inquisition in 1497. There were Rapoports all over Poland and the Baltic states, linked only by place of origin and common fate.