On the way to Marsdon House they went over Davidson’s evidence.

‘It’s a rum thing, when you come to think of it,’ ruminated Fox. ‘There was Sir Daniel looking at that taxi and wishing it wasn’t booked and there inside it were Lord Robert and the man who had made up his mind to kill him. He must have started in to do it almost at once. He hadn’t got much time, after all.’

‘No,’ said Alleyn, ‘the time factor is important.’

‘How exactly d’you reckon he set about it, sir?’

‘I imagine them sitting side by side. The murderer takes out his cigarette-case, if indeed it was a cigarette-case. Perhaps he says something to make Lord Robert lean forward and look through the window. He draws back his hand and hits Lord Robert sharply on the temple with the edge and point of the case—the wound seems to indicate that. Lord Robert slumps back. The murderer presses his muffled hand over the nose and mouth, not too hard but carefully. As the mouth opens he pushes the material he is using between the teeth and further and further back towards the throat. With his other hand he keeps the nostrils closed. And so he sits until they are nearly at Cheyne Walk. When he removes his hands the pulse is still, there is no attempt at respiration. The head falls sideways and he knows it is all over.’ Alleyn clenched his hands. ‘He might have been saved even then, Fox. Artificial respiration might have saved him. But there was the rest of the drive to Queens Gate and then on to the Yard. Hopeless!’

‘The interview with Sir Herbert Carrados ought to clear up this business of Dimitri,’ Fox said. ‘If Sir Herbert was any length of time in the buffet with Dimitri.’

‘We’ll have to go delicately with Carrados. I wonder if the obscure lady will be there. The lady that nobody noticed but who, since she did not dance very much, may have fulfilled the traditional office of the onlooker. Then there’s the Halcut-Hackett game. We’ll have to get on with that as soon as possible. It links up with Withers.’

‘What sort of a lady is Mrs Halcut-Hackett? She came and saw you at the Yard, didn’t she, about the blackmail business?’

‘Yes, Fox, she did. She played the old, old game of pretending to be the friend of the victim. Still she had the pluck to come. That visit of hers marked the beginning of the whole miserable affair. You may be sure that I do not forget this. I asked Bunchy to help us find the blackmailer. If I hadn’t done that he’d be alive now, I suppose, unless … unless, my God! Donald killed his uncle for what he’d get out of it. If blackmail’s at the bottom of the murder, I’m directly responsible.’