‘The blue that was used for the Virgin’s cloak, what they called the azur d’outremer, was the most expensive,’ he continued. ‘A fortune. It was specified in the contract. So much, and no more, to be bought by the painter. It was also spelled out to the artist how he could use it.’ The words were muffled. ‘No artistic freedom in those days. The artist did what he was told.’

While he had been a student at university, he had read up on the subject, claiming it was a relief from the intensity of his main study.

‘A fabulously expensive cloak to wear in the stable,’ she said. ‘Crazy.’

‘Also worn on the flight into Egypt.’ His voice darkened. ‘Watching him on the cross. Taking her dead son in her arms and draping it over him.’

‘Is her cloak ever red or green?’

‘Not at that period. Later, perhaps.’

‘I bet some of the forgers made that mistake.’

Their hands entwined and they were silent until he said, ‘In those days, there was an entire language of colours. Each one had its place in a hierarchy. Everyone understood what they implied in a way that we don’t.’

Later, he sat on the edge of the bed staring out of the window, his hands clasped loosely between his knees. A trace of moisture gleamed on his shoulder blades. She reached out and pressed her finger gently on his spine.

‘The early representations of Mary usually show her with a flat skin tone.’ He turned his head. ‘Unless they were taught by a master, the younger painters did not understand that nothing is flat and smooth. But, as they grew older, and if they were not too arthritic, they learned how to extend the colour range … vermillion, yellow ochre and lead white. Pucelle fils was one of those painters.’

‘How would you paint me?’ she asked softly.

He lay down beside her and propped himself up on an elbow. ‘Grey skin undertones and … yes, blue shadows under the eyes, long brushstrokes to convey your silky skin. I would command the white lead to be ground and I would mix it with just a shade of black bismuth to capture the movement in your face.’ He ran a fingertip over her eyelids. ‘Then I could paint the light in your eyes and expose you: both wary and ecstatic in equal measure.’

She pulled him down to her and kissed him lingeringly and deeply.

Regrets? They would be hammering inside his skull. And, she suspected, the beginnings of hatred for her. Or what she stood for.

The church bells sounded in the distance with a silvery shudder of sound. Vespers. She felt the ripple go through him. Guilt? Longing? She pressed her head against his chest. ‘Go on,’ she said. ‘Say what you always say. What you must.’

He addressed the ceiling. ‘I am … wrong being with you.’