'You are discovered, Brother Edwig,' I called. 'I know about your boat to France! I arrest you in the king's name for theft and murder!'

He darted back inside and I heard his feet pattering away across the boards, accompanied by a metallic chinking sound that puzzled me.

'It's over,' I called. 'There's no other way out of there.' I climbed the last steps and looked in, trying to get a glimpse of him, but from this angle I could see only the floorboards and the great bells beyond the rail. More coins lay scattered around the floor.

I realized this was an impasse; he could not get past me, but I was trapped too. If I were to retreat down the spiral staircase I would be vulnerable to an attack from above and the man I had once taken for a penny-pinching clerk was clearly capable of anything. I advanced into the room, swinging my staff ahead of me.

He was at the other end, behind the bells. He stepped out as I entered and I saw he had two big leather panniers tied together with a thick rope round his neck. The chink of metal sounded from them as he moved. He was breathing hard, brandishing the club in his right hand, the knuckles standing out white and hard.

'What was the plan. Brother?' I called out. 'Take the money from the sales and flee to a new life in France?' I advanced a step, trying to distract him, but he was watchful as a cat and swung the torch threateningly.

'N-no!' He stood there and bawled out the word like a child falsely accused. 'No! This is my fee to enter heaven!'

'What?'

'She refused me and refused me and then the Devil filled my soul with anger and I killed her! Do you know how easy it is to kill someone, Commissioner?' He laughed wildly. 'I saw too much killing as a child, it opened the door to the Devil, always he fills my mind with dreams of b-blood!'

His fat face was scarlet and the veins stood out on his neck as he screamed at me. He had lost control; if I could surprise him, get close enough to ring the bells-

'You'll find it hard to persuade a jury of that,' I called out.

'Pox on your juries!' His stammer vanished as his voice rose to a shout. 'The pope, who is God's vicar on earth, allows the purchase of redemption from sins! I told you, God figures our souls in heaven, the credit balance and the debit! And I will make him such a gift he will take me to his right hand! I am taking almost a thousand pounds to the Church in France, a thousand pounds from the hands of your heretic king. This is a great work in the eyes of God!' He eyed me furiously. 'You will not stop me!'

'Will it buy you forgiveness for Simon and Gabriel too?'

He pointed the torch at me. 'Whelplay guessed what I had done to the girl and would have told you. He had to die, I had to complete my work! And you should have died instead of Gabriel, you crow, God will hold you to account for that!'

'You madman!' I shouted. 'I will see you in the Bedlam, displayed as a warning of what perverted religion can do!'

Then he grasped his club in both hands and ran at me with an eldritch scream. The heavy panniers slowed him or he would have had me, but I managed to dodge aside. He whirled round and swung again. I raised my staff, but he knocked it from my hand with the torch. As it clattered to the floor, I realized he had got himself between me and the door. He advanced slowly, swinging the torch, and I backed up against the low railing separating me from the bells and the great drop below. He was cooler again now; I saw those wicked black eyes calculating the distance between us and the height of the rail. 'Where is your boy?' he asked with an evil grin. 'Not here to protect you today?' Then he flew at me and landed a clout on my arm as I lifted it to defend myself. He pushed me hard in the chest and I fell back, over the low railing.

I still relive that fall in dreams, the sensation of twisting as I fell, my hands grasping at empty air. Always I hear Brother Edwig's triumphant shout in my ears. Then my arms slapped against the side of a bell and instinctively I threw my arms round it, clutching at the metal surface, grinding my fingernails into the ornate design on the surface. It stopped my fall, but my hands were slick with sweat and I felt myself slipping down.

Then my foot hit something and I came to rest. I flattened myself against the bell and managed, just, to link my fingers together around it. Glancing quickly down I saw my foot had come to rest on the plaque on the old Spanish bell. I clung on desperately.

Then I felt the bell start to move. My weight was causing it to swing outwards. It hit the neighbouring bell and a deafening clang echoed through the bell tower as the juddering impact threatened to dislodge me. The bell swung back, with me clinging on like a limpet, and I had a glimpse of Edwig taking off his pannier and bending to the floor to pick up the coins he had dropped, all the while glancing malevolently at me. He knew I could only hold on for moments more. Far below I heard faint voices echoing up; the crowd outside must have run in at the unexpected peal of the bell. I dared not look down. The bell swung back and hit its neighbour again; this time it set the whole lot clanging with a noise I thought would burst my ears and now as the bell vibrated with the impact I felt my hands slipping apart.

Then I did the most desperate thing I have ever done in my life. I only made the attempt because I knew the alternative was certain death. In a single movement I let my hands fall apart, twisted in the air and used my foot against the plaque as leverage to hurl myself outwards, towards the rail, commending my soul to God in what I knew was probably my final thought on earth.

I hit the rail with my midriff, knocking the breath from my body. It shook with the impact as my frantic hands grasped the inner side and I hauled myself over, how I do not know. Then I was lying on the floor in a heap, my back and arms an agony, as across the room Edwig knelt clutching a handful of coins, staring at me in angry bafflement as the clangour of the bells rang and sang in our ears, the vibration now shaking the very floorboards.

He was up in an instant, grabbing for his panniers and running for the door. I threw myself at him, clutching for his eyes. He thrust me off, but was thrown off balance by the weight of the bags. He staggered and came up against the rail as I had done a minute before. As he did so he dropped his leather bags. They fell over the edge, and with a cry he leaned over and snatched at the rope holding them together. He caught hold, but the movement overbalanced him. For a moment he lay spreadeagled across the rails and I believe that if he had let go the gold he might have saved himself, but he held on. The bags' weight tipped him forward and he fell over head first, bouncing off the side of a bell and disappearing from view with a scream of terrified anger, as though in his last moment he knew he faced his Maker before he had made his great gift. I ran to the parapet and saw him still falling, his habit billowing out around him as he spun to earth in the middle of a great shower of coins from the panniers. The crowd fled in panic as he hit the ground in an explosion of blood and gold.

I leaned over the rail, panting and sweating, watching as the crowd slowly crept in again. Some looked down at the bursar's remains, others peered up to where I stood. To my disgust I saw monks and servants get down on hands and knees and begin scrabbling on the floor, grabbing up handfuls of coins.