Cranston touched him on the arm and pointed to the far corner, just past the huge gateway. An emaciated fellow with jet black hair, thin lips and large brooding eyes caught the friar’s eye. The man was dressed completely in black, his dark cloak covered with the most fantastic symbols: pentangles, stars, moons, suns, and on his head a pointed hat. He had laid out a great canvas sheet before him, bearing different phials and small bowls. Now he stood still, his very appearance drawing the people around him.

‘Watch this!’ Cranston whispered. ‘The fellow’s our guide.’

The man took out two small whistles and, pushing one into each corner of his mouth, began to play a strange, rhythmic, haunting tune. He then put down the instruments and held up powerful hands.

‘Ladies and gentlemen, knights, courtiers, members of the Guild!’ He caught Athelstan’s eye. ‘Friars, priests, citizens of London! I am Doctor Mirablis. I have studied in Byzantium and Trezibond, and travelled across the land to the great Cham of Tartary. I have seen battle fleets in the Black Sea and the great war galleons of the Caspian. I have supped with the Golden Horde of Genghis Khan. I have crossed deserts, visited fabulous cities, and in my journeys I have amassed many secrets and mysteries!’

His claims were greeted with roars of laughter. Cranston and Athelstan drew closer. An apprentice from a nearby stall took out a bullock horn, scooped some dirty water from a rain barrel and began to sprinkle the magician with it. Dr Mirabilis just ignored him and held up his hands, calming the clamour and good natured catcalls.

‘I will show you I have power over matter. Over the very birds in the air.’ He turned, pointing up to the top of the monastery wall. ‘See that pigeon there!’ Everyone’s eyes followed the direction of his finger. ‘Now, look,’ the fellow continued, and taking a piece of black charcoal, painted a rough picture of the bird on the monastery wall. He then began to stab the drawing, uttering magical incantations. The clamour grew around him, Cranston and Athelstan moved closer, their hands on their wallets as the crowd was infested with naps, foists and pickpockets as a rick of hay with mice and rats. Mirabilis continued to stab the picture, muttering low-voiced curses, looking up at the walls where the pigeon was still standing. Suddenly the bird, as if influenced by the magical incantations against the picture below, twitched and dropped down dead. The ‘oohs’ and ‘ahs’ of reverence which greeted this would have been the envy of any priest or preacher. Cranston grinned and gripped Athelstan by the wrist.

‘Wait awhile,’ he said.

Doctor Mirabilis’s reputation now enhanced by this miracle, he began to sell his jars and philtres of crushed diamond, skin of newt collected at midnight, batwing, marjoram, fennel and hyssop.

‘Certain cures,’ he said, ‘for any agues, aches and rheums you suffer from.’