‘Oh God,’ said Alleyn, ‘once the wheels begin to turn, it’s easier to forget the other side. If only I didn’t see him so often. He looked like a child, Fox. Just like a child.’

‘Yes,’ said Fox. ‘It’s a nasty case, personal feelings aside. If you see the Assistant Commissioner now, Mr Alleyn, I’ll be ready to join you for a bite of lunch before we go to Sir Daniel Davidson’s.’

‘All right, blast you. Meet me downstairs in a quarter of an hour.’

‘Thank you, sir,’ said Fox. ‘I’ll be pleased.’

About twenty minutes later he presided over Alleyn’s lunch, with all the tranquil superiority of a nannie. They arrived at St. Luke’s Chambers, Harley Street, at two o’clock precisely. They sat in a waiting-room lavishly strewn with new periodicals. Fox solemnly read Punch, while Alleyn, with every appearance of the politest attention, looked at a brochure appealing for clothes and money for the Central Chinese Medical Mission. In a minute or two a secretary told them that Sir Daniel would see them and showed them into his consulting-room.

‘The gentlemen from Scotland Yard, Sir Daniel. Mr Alleyn and Mr Fox.’

Davidson, who had apparently been staring out of the window, came forward and shook hands.

‘It’s very good of you to come to me,’ he said. ‘I said on the telephone that I was quite ready to report at Scotland Yard whenever it suited you. Do sit down.’

They sat down. Alleyn glanced round the room and what he saw pleased him. It was a charming room with apple-green walls, an Adam fireplace and silver-starred curtains. Above the mantelpiece hung a sunny landscape by a famous painter. A silk praying-mat that would not have disgraced a collector’s walls did workaday service before the fireplace. Sir Daniel’s desk was an adapted spinet, his inkwell recalled the days when sanded paper was inscribed with high-sounding phrases in quill-scratched calligraphy. As he sat at his desk Sir Daniel saw before him in Chinese ceramic, a little rose-red horse. A beautiful and expensive room, crying in devious tones of the gratitude of wealthy patients. The most exalted, if not the richest, of these stared with blank magnificence from a silver frame.

Sir Daniel himself, neat, exquisite in London clothes and a slightly flamboyant tie, with something a little exotic about his fine dark head, looked as though he could have no other setting than this. He seated himself at his desk, joined his hands and contemplated Alleyn with frank curiosity.

‘Surely you are Roderick Alleyn?’ he said.

‘Yes.’

‘I have read your book.’

‘Are you interested in criminology?’ asked Alleyn with a smile.

‘Enormously! I hardly dare to tell you this because you must so often fall a victim to the enthusiasm of fools. I, too! “Oh, Sir Daniel, it must be too marvellous to be able to look into the minds of people as you do.” Their minds! My God! Their stomachs are enough. But I often think quite seriously that I should have liked to follow medical jurisprudence.’