He nodded slowly. 'No, that's what I've been told. You've lost the fire for our cause but you've not turned enemy, which is more than can be said for some. So a new weapon, something that could make our ships invincible, you can see how important that could be.'

'Yes, but-' I hesitated.

'Go on.'

'My lord, sometimes in desperate times we clutch at desperate remedies. The alchemists have promised us wonders for hundreds of years, but precious few have actually appeared.'

He nodded approvingly. 'Good, Matthew, you could ever put your finger on a weak point in an argument. But, remember, I've seen it. I met the Gristwoods here and told them I'd arrange for an old crayer to be floated up to an abandoned jetty at Deptford early one morning and, if they could destroy it with Greek Fire in front of me, I'd make a deal with them. Jack arranged it all, and only he and I and they were present early one morning at the start of the month. And they did it.' He spread his arms wide and shook his head. I could see that he was still amazed by what he had seen.

'They brought some strange device of steel they'd made with them, with a pipe on a pivot. They operated a pump on the device – and then a great sheet of liquid flame shot out and consumed the old boat in minutes. When I saw it I nearly fell in the water. It wasn't an explosion, like gunpowder, just' – he shook his head again – 'an inextinguishable fire, more fast and furious than any fire I've seen. Like a dragon's breath. And with no incantations, Matthew, no magic words. This is no trick, it's something new; or, rather, something ancient rediscovered. I had a second demonstration a week later; they did it again. So now I've told the king.'

I glanced at Grey, who nodded at me seriously. Cromwell took a deep breath.

'He was more enthusiastic than I'd dared to hope. You should have seen his eyes light up. He clapped me on the shoulder, and he's not done that in a long while. He asked for a demonstration before him. There's an old warship, the Grace of God, in Deptford for breaking up. I've arranged for it to be there on the tenth of June, in twelve days' time.' The tenth of June, I thought, the day Elizabeth's period of grace expires.

'I've been caught unawares,' he went on. 'I didn't think the king would jump at it so quickly. I can't fence with the Gristwoods any more. I must have that formula in my hands, and the Greek Fire they've made, before the king sees that demonstration. I want you to get it from them.'

I breathed heavily. 'I see.'

'It's only a matter of persuasion, Matthew. Michael Gristwood knows you and respects you. If you remind him the formula is legally the king's and tell him the king is personally involved, I think you can make him believe you, and give you the formula. I want it done then and there. Jack has a hundred pounds in gold angels about him that Gristwood is to have as a reward. And you can warn him that if he doesn't cooperate I can call the Tower's rack to my aid.'

I looked up at him. My head swam at the thought of becoming involved in a matter that concerned the king himself, but Cromwell had Elizabeth's life in his hands. I took a deep breath.

'Where does Gristwood live?'

'Sepultus and Michael live with Michael's wife in a big old house in Wolf's Lane, in the parish of Allhallows the Less in Queenhithe. Sepultus works from there. I want you to go there today. Jack will accompany you.'

'I beg this may be all. I live quietly these days, that is all I wish to do.'

I expected harsh words for my weakness, but Cromwell only smiled wryly. 'Yes, Matthew, after this you may go back to your quiet.' He looked at me fixedly. 'Be grateful you have the chance.'

'Thank you, my lord.'

He stood up. 'Then go now, ride to Queenhithe. If the Gristwoods are not there, find them. Jack, I want you back here by the end of the day.'

'Yes, my lord.'

I rose and bowed. Barak rose and opened the door. Before I followed him I turned back to my old master.

'May I ask, my lord: why did you choose me for this?' From the corner of my eye, I saw Grey give me a slight shake of the head.

Cromwell inclined his head. 'Because Gristwood knows you for an honest man and will trust you. As I do because I know you are one of the few who would not seek to make advantage for themselves from this. You are too honest.'

'Thank you,' I said quietly.

His face hardened. 'And because you care too much for the fate of the Wentworth girl and, finally, you are too afraid of me to dare cross me.'

OUTSIDE, BARAK TOLD ME brusquely to wait while he fetched the horses. I stood on the steps of the Domus, looking out across Chancery Lane. For a second time Cromwell had casually dropped me into an affair with dangerous ramifications. But there was nothing I could do; even if I had dared defy him, there remained Elizabeth.

Barak reappeared, riding his black mare and leading Chancery. I mounted and we rode to the gate. His expression was closed, serious. Barak, I thought, what sort of a name was that? It wasn't English, though he seemed English enough.

We had to pause in the gateway as a long procession of sulky looking apprentices wearing the blue and red badges of the Leathersellers' Company marched past. Longbows were slung over their shoulders, and a few carried long matchlock guns. Because of the invasion threat, all young men now had to undertake compulsory military practice. They passed up towards Holborn Fields.

We rode downhill to the City. 'So you were at the scene of this demonstration of Greek Fire, Barak?' I said, adopting a deliberately haughty tone; I had decided I was not going to be intimidated by this rude young fellow.

'Keep your voice down.' He gave me a frowning look. 'We don't want that name bandied abroad. Yes, I was there. And it was as the earl said. I would not have believed it had I not seen it.'

'Many wonderful tricks may be performed with gunpowder. At the last mayor's procession there was a dragon that spat balls of exploding fire-'

'D'you think I don't know a gunpowder trick when I see one? What happened at Deptford was different. It wasn't gunpowder: it was like nothing that's been seen before, in England, anyway.' He turned away, steering his horse through the crowds going through the Ludgate.

We rode along Thames Street, our progress slow through the lunchtime crowds. It was the hottest time of the day and Chancery was sweating and uncomfortable. I felt sunburn prickling on my cheeks and coughed as a swirl of dust went into my mouth.

'Not far now,' Barak said. 'We turn down to the river soon.'

I voiced a thought which had occurred to me. 'I wonder why Gristwood did not approach Lord Cromwell through Sir Richard Rich. He's Chancellor of Augmentations.'

'He wouldn't trust Rich. Everyone knows what a rogue he is. Rich would have kept the formula and bargained with it himself, and probably dismissed Gristwood into the bargain.'

I nodded. Sir Richard was a brilliant lawyer and administrator, but he was said to be the most cruel and unscrupulous man in England.

We entered the maze of narrow streets leading down to the Thames. I glimpsed the river, its brown waters alive with wherries and white-sailed tilt boats, but the breeze that came from it was tainted; the tide was still out, the filth-strewn mud stewing in the sun.

Wolf's Lane was a long narrow street full of old houses, decayed-looking cheap shops and lodging places. Outside one of the larger houses I saw a brightly painted sign which showed Adam and Eve standing on either side of the philosopher's egg, the legendary sealed vase in which base metal could be turned to gold, an alchemist's sign. The place was in dire need of repair, plaster was peeling from the walls and the overhanging roof lacked several tiles. Like many houses built on Thames mud, it had a pronounced tilt to one side.