'No, it cannot have been.'

'And you saw no one on your way to the kitchen?'

'No.'

I was pleased to find my brain working again, my mind racing along. 'Whoever killed Singleton would himself have been covered in blood. He would have had bloody clothes, left bloody footsteps.'

'I saw none. But I confess it was not in my mind to look, I was shocked. Later, of course, when the house was roused, there were bloody footprints everywhere from those who had entered the kitchen.'

I thought a moment. 'And the killer may then have gone to the church, desecrated the altar and stolen the relic. Did you, did anyone, notice any traces of blood on the way across the cloister to the church, or inside the church?'

Brother Guy gave me a sombre look. 'There was blood spilt about the church. We assumed it came from that sacrificed cock. As for the cloister, it started to rain before dawn and went on all day. It would have washed away any traces.'

'And after you found the body, what did you do?'

'I went straight to the abbot, of course. Now, here we are.'

He had led us to the largest of the crypts, a one-storey building in the ubiquitous yellow limestone, set on a little rise. It had a stout wooden door, wide enough for a coffin to be carried in.

I blinked a snowflake from my eyelashes. 'Well, let us get this over with.' He produced a key and I took a deep breath, breathing a silent prayer that God might strengthen my weak stomach.

We had to stoop to enter the low, whitewashed chamber. The ossuary was bitterly cold, the wind slicing in through a small barred window. The air held the faint, sickly tang all tombs possess. In the dim light of Brother Guy's lamp I saw the walls were lined with stone sarcophagi, figures representing the dead carved atop the lids, hands clasped in poses of supplication. Most of the men wore the full armour of past centuries.

Brother Guy put his lamp down and folded his arms, tucking his hands inside the long sleeves of his habit for warmth. 'The Fitzhugh crypt,' he said. 'The family were the original founders of the monastery and were buried here till the last of them died in the civil wars of the last century.'

The silence was suddenly broken by a jangling metallic crash. I jumped involuntarily and so did Brother Guy, his eyes wide in his dark face. I turned to see Mark bent over, picking the abbot's bunch of keys from the flagstones.

'I'm sorry, sir,' he muttered. 'I thought they were securely tied.'

'God's death!' I snapped. 'Oaf!' My legs were shaking.

There was a large metal sconce filled with fat candles in the centre of the room. Brother Guy lit them from his lamp and a yellow glow filled the chamber as he led us across to a sarcophagus with a bare stone lid, without inscription.

'"This tomb is the only one without a permanent occupant and will never have one now. The last male heir perished at Bosworth with King Richard III."' He smiled sadly. '"Sic transit gloria mundi."'

'And Singleton is laid there?' I asked.

He nodded. 'He's been there four days, but the cold should have kept him fresh.'

I took another deep breath. 'Then let us have the lid off. Mark, help him.'

Mark and Brother Guy strained to slide the heavy stone lid onto the neighbouring tomb. It resisted their efforts at first, then slid off in a rush. At once the chamber was filled with a sickening smell. Mark stepped back a pace, his nose wrinkling with distaste. 'Not so fresh,' he murmured.

Brother Guy peered in, crossing himself. I stepped forward, gripping the edge of the sarcophagus.

The body was wrapped in a white woollen cloth; only the calves and feet were visible, alabaster white, the toenails long and yellow. At the other end of the blanket a little watery blood had run out from the neck, and there was a pool of darker blood under the head, which had been set upright beside the body. I looked into the face of Robin Singleton, whom once I had outstared across the courtroom.

He had been a thin man in his thirties, with black hair and a long nose. I saw there was a dark stubble on the white cheeks and felt my stomach turn at the sight of this head set upon a bloody piece of stone instead of a neck. The mouth was almost closed, the tips of the teeth showing under the lips. The dark-blue eyes were wide open, filmy in death. I saw a tiny black insect walk from under one eyelid across the orb and under the opposite lid. Swallowing, I turned and stepped over to the little barred window, taking a deep breath of cold night air. As I fought down bile, I forced another part of my mind to order what I had seen. I heard Mark come to my side.

'Are you all right, sir?'

'Of course.' Turning, I saw Brother Guy standing with arms folded, quite composed, looking at me thoughtfully. Mark himself was a little pale, but crossed back to look again at that dreadful head.

'Well, Mark, what would you say about the manner of that man's death?' I called.

He shook his head. 'It is as we knew, his head was struck from his shoulders.'

'I didn't think he died from an ague. But can we tell anything more from what is there? I would take a guess that the assailant was of at least medium height, to start with.'

Brother Guy looked at me curiously. 'How can you say that?'

'Well, firstly, Singleton was quite a tall man.'

'It's hard to tell without a head,' Mark said.

'I met him in court. I remember I had the disadvantage of having to twist my neck to look up at him.' I made myself go over and look at the head again. 'And see how the neck is cut straight across. It sits perfectly upright on the stone. If he and his attacker were both standing when he was attacked, which seems most likely, a shorter man would have had to strike upwards at an angle, and the neck would not have been cut straight through.'

Brother Guy nodded. 'That is true. By Our Lady, sir, you have the eye of a physician.'

'Thank you. Though I would not wish to spend my days looking on such sights. But I have seen a head severed before. I remember the-' I sought a word – 'the mechanics.' I met the infirmarian's curious gaze, digging my fingernails into my palms as I remembered a day I wished dearly to forget. 'And, talking of such matters, observe how clean the blow is, the head sheared off with one strike. That is difficult to achieve even if someone is lying down with his neck on a block.'

Mark looked again at the head lying on its side, and nodded once more. 'Aye. Axes are difficult to handle. I was told they had to hack away at Thomas More's neck. But what if he was bending down? To pick something up from the floor? Or perhaps he was made to bend down?'

I thought a moment. 'Yes. Good point. But if he was bent over as he died the body would have been bent when it was found. Brother Guy will remember.' I looked at him enquiringly.

'He lay straight,' the infirmarian said thoughtfully. 'The difficulty of striking off someone's head like that has been in all our minds. You couldn't do it with a kitchen implement, even the biggest knife. That is why some of the brothers fear witchcraft.'

'But what weapon could slice the head off a man standing upright?' I asked. 'I'd guess not an axe, the blade is too thick. You'd need a very sharp cutting edge, like a sword. In fact I can't think of anything that would do it but a sword. What do you say, Mark? You're the swordsman here.'

'I think you are right.' He gave a nervous laugh. 'Only royalty and the nobility have the right to be executed with a sword.'

'Precisely because a sharp sword blade ensures a swift end.'

'Like Anne Boleyn,' Mark said.

Brother Guy crossed himself. 'The witch queen,' he said quietly.

'That is what brought it to mind,' I said softly. 'The one beheading I have seen. Just like Anne Boleyn.'