He said: ‘It’s a difficult decision. If you go back to London I’m afraid I shall be obliged to keep in touch and bother you with questions and you may have to return. There will be an inquest, of course. I don’t know if you will be called. You may be.’

‘With whom does the decision rest?’

‘Primarily, with the police.’

‘With you, then?’

‘Yes. It rests upon our report. Usually the witnesses called at an inquest are the persons who found the body; me, in this instance, together with the investigating officers, the pathologist and anyone who saw or spoke to the deceased shortly before the event. Or anyone else who the police believe can throw light on the circumstances. Do you think,’ he asked, ‘you can do that?’

Miss Emily looked disconcerted. It was the first time, he thought, that he had ever seen her at a loss.

‘No,’ she said. ‘I think not.’

‘Miss Emily, do you believe that Wally Trehern came back after you had left the enclosure, saw Miss Cost under her umbrella, crept up to the boulder by a roundabout way (there’s plenty of cover) and threw down the rock, thinking he threw it on you?’

‘How could that be? How could he get in? The enclosure was locked.’

‘He may have had a disc, you know.’

‘What would be done to him?’

‘Nothing very dreadful. He would probably be sent to an institution.’

She moved about the room with an air of indecision that reminded him, disturbingly, of Mrs Barrimore. ‘I can only repeat,’ she said at last, ‘what I know. I saw him. He cried out and then hid himself. That is all.’

‘I think we may ask you to speak of that at the inquest.’

‘And in the meantime?’

‘In the meantime, perhaps we should compromise. There is, I’m told, a reasonably good hotel in the hills outside Dunlowman. If I can arrange for you to stay there, will you do so? The inquest may be held at Dunlowman. It would be less of a fuss for you than returning from London.’

‘It’s inadvisable for me to remain here?’

‘Very inadvisable.’

‘So be it,’ said Miss Emily. His relief was tempered by a great uneasiness. He had never known her so tractable before.

‘I’ll telephone the hotel,’ he said. ‘And Troy, if I may,’ he added with a sigh.

‘Had I taken your advice and remained in London, this would not have happened.’