‘He is awake now.’

‘He’s like a wakeful child now. He has a dream of harmony and peace and then he will fall asleep again, smiling at his lovely dream.’

I pause. I know she is right. The king has slipped through to another world and we need him in this one. ‘I will come with you. But if I think your alchemist is a charlatan, I will have no truck with him.’

‘That’s the very reason I want you to come,’ she says. ‘To see what you think of him. But come now.’

We go on foot, through the darkened streets of Westminster, hand in hand. We have no ladies in waiting, not even a guard. For one moment only, I close my eyes in horror at what Richard my husband would say if he knew that I was taking such a risk and with the queen herself. But she knows where she is going. Sure-footed on the muck of the streets, imperious to the crossing-sweepers, with a little lad going ahead of us with a flaming torch, she guides us down the narrow lanes, and turns into an alley. At the end of it is a great door set in the wall.

I take the iron ring set beside it, and pull. A great carillon answers us, and the sound of dogs barking somewhere at the back. The porter opens the grille. ‘Who calls?’ he asks.

Margaret steps up. ‘Tell your master that she of Anjou has come,’ she says.

At once the door swings open. She beckons to me, and we go inside. We step into a forest, not a garden. It is like a plantation of fir trees inside the tall walls, in the very heart of London, a secret woodland like a London garden under an enchantment to grow wild. I glance at Margaret and she smiles at me as if she knows how this place will strike me: as a hidden world within the real one; perhaps it is even the doorway to another world inside this.

We walk down a twisting path which takes us through the green shadow of towering trees and then to a small house, overburdened with dark trees around it, sweet-scented boughs leaning on every roof, chimneys poking through foliage and singeing the needles of the pine trees. I sniff the air, there is the smell of a forge, thin smoke from hot coals, and the familiar, never-forgotten scent of sulphur. ‘He lives here,’ I say.

She nods. ‘You will see him. You can judge for yourself.’

We wait, beside a stone bench before the house, and then a little door swings open and the alchemist comes out, a dark cloak around him, wiping his hands on his sleeves. He bows to the queen and directs a piercing look at me.

‘You are of the House of Melusina?’ he asks me.

‘I am Lady Rivers now,’ I say.

‘I have long wanted to meet you. I knew Master Forte, who worked for your husband the duke. He told me that you had the gift of scrying.’