It was only with the last notes of the Polonaise that the pair gave way to elation, laughing like the two children in a secret garden that they still were, behind their arthritic joints and painful tendons. Tovey whirled round on his revolving piano stool three times for joy. ‘You see what a splendid job Hindemith has made of it!’ he said. ‘You can trust every note.’

‘It’s not all Hindemith,’ Jelly smiled. ‘Some of the violin part is me. With a little, er, help. We’ve tried to make some… adjustments.’

‘We?’

‘The spirits and me.’

‘What?’ Tovey looked genuinely shocked. ‘Are you serious?’

‘They are incredible. They tell me everything, advise on everything.’

‘And they are who?’

‘Onkel Jo and Schumann, or their messengers, as we understand.’

‘Oh Jelly, Jelly… ’ He shook his head.

‘But that’s what happened – and you like what we’ve done. You just said so.’

Tovey leafed through the pages on his piano, apparently pondering her words. ‘All right,’ he said, finally. ‘So, tomorrow we’ll sit down and make sure you’re happy with every last second of it.’

Jelly was quietly relieved: she knew she still needed his expertise in analysing and perfecting the details.

‘This passage – it reminds me of something, I can’t place it… ’ She picked out the second theme of the first movement, the one that finally transforms into the Polonaise.

‘Could it be this?’ Tovey began to play another melody, one that she knew very well: the Brahms Violin Concerto, again the second theme of the first movement. The motif stood out: the same pattern, almost a twin to Schumann’s. This time, though, it seemed to link the wide swoops of the melody rather than making a statement in its own right.

‘You mean Brahms used Schumann’s theme? When did Brahms write his concerto?’

‘About 1878,’ said Tovey. ‘Twenty-two years after Schumann died.’

‘So – would he have heard Schumann’s, or looked at the manuscript?’

‘It’s perfectly possible, given Brahms’s astonishing brain, that he retained the impression of that melody, having seen it only once. I wouldn’t put it past him. Whether he viewed the manuscript again – well, who can say?’

‘But you think it’s deliberately done?’