Joe produced a paper evidence bag from his pocket and held it open to receive the stub. ‘Not an enthusiastic smoker, evidently. Only a few puffs taken before she threw it away. Interrupted by the arrival of the taxi?’

‘Who do you know who smokes Balkan Sobranie, Holmes?’ Lily asked, laughing at him. She seemed to have been suddenly ambushed by their ridiculous situation.

He answered the question with a grimace: ‘Ah! If only it were so simple in real life. Balkan Sobranie, eh? You’re right. That would reduce our smoker to a select club of about ten thousand émigré Russians and as many Londoners who think it the smart thing to do. Anyone from a grand duchess who screws one into a six-inch-long Fabergé holder to the girlfriend of a Soho waiter who’s decided to have a flirt with the bohemian style.’ He sighed. ‘Still — worth recording and preserving. Perhaps Miss Hampshire will be able to throw a little light? I must check the plans Hopkirk has for re-interviewing that lady.’

‘We’re thinking the same thing, sir? On the same lines as Lady Dedham herself? She was convinced it was a third gun that fired the finishing shot from across the road. And we’re looking at evidence of a third party present at the scene.’

Joe nodded. ‘Yes. Interesting that in all the noise and horror Cassandra picked out a third gun. A killer still at large? I’ll tell you — while you two were upstairs, Hopkirk read out to me over the telephone the initial report from the autopsy. Dr Spilsbury had interesting things to say …’ He took out a notebook and found his place. ‘I give you the salient bits … Hit, in the first instance, by two bullets fired one from the left and one from the right at a distance of no more than six feet. One narrowly missed the lung and crossed the body to lodge in the muscle under his left arm, the other shot penetrated a lung and would, ultimately, have caused death. The coup de grâce was delivered from farther afield and from a higher-calibre gun. Something in the order of a Browning. In the hands of a marksman, I’m inferring from the doc’s comments. Clean shot through the heart. He was dead in seconds.

‘The first two shots came from guns identified as Webleys. As issued by the British army. Thousands of those about on the quiet in London. Old soldiers sometimes fail to turn their weapons in. Conveniently “lose” them. They get used to having protection to hand and can’t bear to give them up. Who am I to blame them — I have an illicit Luger at home myself.’

‘Have you any idea of the distance?’ Lily asked. ‘Of the lethal shot?’

‘Spilsbury’s estimate from an examination of the wound would place the gunman at the edge of the road, right where the taxi was parked.’

‘By someone standing behind and using the motor for cover? Inside it and firing from a window? Or someone at the wheel?’

‘As you say. I think we’ve finished here for the time being, Wentworth. Right — what do you fancy next? Shall I take you to view the wounded at the hospital? I can offer you the butler or the driver, though he was still unconscious when last I heard.’