For a while business was brisk, then the crowd drifted away to watch an old man further down the lane who cavorted and danced in the most fantastical way. Cranston handed the reins of his horse to Athelstan and went over to the ‘doctor.’

‘Most Reverend Doctor Mirabilis, it is good to meet you again.’

The fellow looked up, his eyes milky blue like those of a cat. He studied Cranston then stared past him at Athelstan.

‘Do I know you?’ he asked. ‘Do you wish to buy my physic?’

‘Samuel Parrot,’ continued Cranston, ‘I would not buy green grass from you in the spring.’

The fellow’s eyes shifted to right and left.

‘Who are you?’ he whispered.

‘Surely you have not forgotten me, Mirabilis?’ Cranston murmured. ‘A certain case before the Justices in the Guildhall about physic which was supposed to cure. Instead, it made men and women sick for weeks.’

The famous Doctor Mirabilis stepped closer.

‘Of course!’ His face broke into a gap-toothed smile. ‘Sir John Cranston, coroner!’ The smile was hideously false. ‘Is there anything I can do for you?’

‘Not here,’ Cranston said. ‘But Piper Alley, Nightshade House. You can lead us there?’

The physician nodded and, scooping up his philtres and potions into a leather sheet, led Cranston and Athelstan from Whitefriars down a maze of streets so narrow they continued to lead their horses.

‘How does he do it?’ Athelstan whispered.

‘Do what?’

‘The bird, the pigeon?’

Cranston laughed and gestured to where Doctor Mirabilis was now walking ahead of them.

‘If you went to his little garret, you would find baskets of trained pigeons - you know, the type which carries messages. Every so often our friend here drugs one of them with nox vomica, a slow acting poison. The pigeon is released and takes up a stance nearby. The poor bird will remain immobile because of the effects of the poison. After a while it will drop down dead, and there you have his magic!’ He laughed. ‘Sometimes, of course, it does not work. Doctor Mirabilis here is always ready to run, fleet as a deer, fast as any hare!’

The learned physician, as if he knew his name was being mentioned, turned and gave a gap-toothed grin, waving at them to follow a little faster.