‘What may at first look tiresome,’ Alleyn went on ‘is the position of the three decapitated daisy stalks and their heads. It’s true that one swipe of a suitable instrument might have beheaded all three and landed one daisy on the Colonel, a second on the bank and a third in the punt. Fair enough. But the same swipe couldn’t have reached the Colonel himself.’

Oliphant stared pointedly at the pole lying in the punt.

‘No, Oliphant,’ Alleyn said. ‘You try standing in this punt, whirling that thing round your head, swishing it through the daisies and catching a squatting man neatly on the temple with the end. What do you think our killer is – a caber-tosser from Braemar?’

‘Do you reckon then,’ Fox said, ‘that the daisies were beheaded by a second blow or earlier in the day? Or something?’

Sergeant Oliphant suddenly remarked: ‘Pardon me, but did the daisies necessairily have anything to do with the crime?’

‘I think there’s probably a connection,’ Alleyn rejoined, giving the sergeant his full attention. ‘The three heads are fresh enough to suggest it. One was in the Colonel’s coat and one was in the punt.’

‘Well, pardon me, sir,’ the emboldened sergeant continued with a slight modulation of his theme; ‘but did the punt necessairily have any bearing on the crime?’

‘Unless we find a left-handed suspect I think we must accept the punt as a working hypothesis. Have a look at the area between the punt and the place where the body lay, and the patch of stones between the tuft from which the grass was cut and the place where the fish lay. It would be possible to step from the punt on to that patch of stones and you would then be standing close to the position of Colonel Cartarette’s head. You would leave little or no trace of your presence. Now, on the willow grove side of the body, the ground is soft and earthy. The Colonel himself, Nurse Kettle and Dr Lacklander have all left recognizable prints there. But there are no traces of a fourth visitor. Accept for the moment the theory that, after the Colonel had been knocked out, our assailant did step ashore on to the stony patch to deliver the final injury or perhaps merely to make sure the victim was already dead. How would such a theory fit in with the missing trout, the punt and the daisies?’

Alleyn looked from Oliphant to Fox. The former had assumed that air of portentousness that so often waits upon utter bewilderment. The latter merely looked mildly astonished. This expression indicated that Mr Fox had caught on.

Alleyn elaborated his theory of the trout, the punt and the daisies, building up a complete and detailed picture of one way in which Colonel Cartarette might have been murdered. ‘I realize,’ he said, ‘that it’s all as full of “ifs” as a passport to paradise. Produce any other theory that fits the facts and I’ll embrace it with fervour.’