Again they pressed, watching the small door close when Athelstan pushed the apple between the serpent and Eve. He pushed and it re-opened. Slowly they approached the cavity, each trying to control his excitement. Athelstan put his hand gingerly into the small, dark space and brought out two rolls of parchment. He ignored Cranston’s excited pleas to hurry and went over to the window, unrolling them carefully. The first was a love poem written in a rough hand in Norman French. At first Athelstan thought it was addressed to a woman but realised it was written to a young man. He handed it over to Cranston.

‘Make of that what you wish!’

The second was a small indenture or agreement. The top was perforated, so someone else must have a copy. Athelstan read and knew why John of Gaunt, Duke of Lancaster, was so indebted to Sir Thomas Springall, and why the merchant had possessed secrets which could have brought him even greater wealth. Cranston had already dismissed the poem, but when he read the indenture he sat at the foot of the bed stupefied, the parchment held loosely between his fingers.

‘This was written fourteen months ago,’ he said quietly. ‘As the Black Prince, father of the present king, lay dying. If the Lord Edward had known this, he would have had John of Gaunt’s head on a pole on London Bridge. If it was revealed now there would be a public outcry.’

‘So we know the reasons for Springall’s death,’ Athelstan said, ‘but not the hows, the wherefores, and above all the culprit or culprits. Look, Sir John, let’s follow the method of the Schools at Oxford. You sit on the bed, I’ll sit beside you. You will recite everything you know about each of the four murders, beginning with Sir Thomas Springall’s. Though in fact there was another killing, making five in all.’ He pointed to the parchment poem. ‘The young boy who died here must also be regarded as a victim.’

And so they began, Cranston occasionally pausing for refreshment as he recited in an almost sing-song voice what they knew about Springall’s death, and then Brampton’s, Vechey’s and Allingham’s. Athelstan would correct him and make Cranston repeat the list of facts time and again until the coroner, not famous for his patience, shouted: ‘Hell’s teeth! What are you doing, Brother? We are wasting time! All we are doing is repeating what we already know.’

‘Be patient, Sir John,’ Athelstan replied, ‘Remember, we are looking for a pattern. In logic when you have a problem, the very words of the puzzle contain the answer. There must be a pattern in each of the murders.’ He saw Sir John set his mouth and glare from beneath bushy grey eyebrows. ‘Look, there is one murder we know very little about - Vechey’s. But three, Allingham’s, Brampton’s and Springall’s, we do. There must be common factors, things which link all three. We have already established one: poison. I also suspect Vechey and Brampton were drugged. They would not have allowed people to pluck them up, take them prisoner, tie a noose around their necks and kill them. So we have some matching strands. Let us see if there are more.’