‘Mr Austin Ponson and Sir William!’ The sergeant reached his climax with an air of triumph.

Tanner was genuinely surprised.

‘Couldn’t have been,’ he said after a moment. ‘I went into all that. Mr Austin was half-way to the Abbey ruins at that time.’

‘She was quite certain, and she said the man Potts was certain too.’

‘Have you seen him?’

‘No, sir. He is a bookseller’s assistant in London—to Evans & Hope, in Paternoster Row. His people live here, and he was down on a couple of days’ holidays.’

Tanner noted the address.

‘How was Mr Austin supposed to be dressed?’

‘In bluish grey clothes that looked like flannel, and a white straw hat.’

‘And Sir William?’