‘Sir!’ Lily spoke swiftly. ‘Again, his wife has an explanation. No sinister political motive involved – she claimed that he was seeking proximity for purposes of social aggrandizement. He just wanted his photo in the press … posing with the prince, on the front page of the society journals.’

Rupert groaned. ‘They will do it! I’ll make that steward account for the bulge in his back pocket.’

Sandilands nodded and carried on. ‘Now here’s a view of the table as it was at the moment Prince Gustavus sank gargling from view on the far side. The plates and glasses – I want you to consider them. The contents have been bagged and bottled and are at present at the lab undergoing the usual tests. Rupert – take us through it.’

‘The far side, where you see a half-full glass of wine, was the POW’s place. Next to him, on his right hand, where you see an empty glass, was the place Miss Wentworth had originally occupied. In her absence, Gustavus, finding the effort of shouting in Serbian from his original place over the table too demanding, had sidled round, taking his glass with him, and plonked himself in Wentworth’s vacated seat. He had previously turned down offers to have food fetched but had consumed a quantity of wine.’

Sandilands took over. ‘Aided in his consumption by the copious amounts poured out for him by Fanshawe here. What exactly were you hoping to achieve by that, Fanshawe?’

‘I thought I’d achieved my end, sir.’ Fanshawe’s tone was truculent and resentful. ‘I was trying to incapacitate the ghastly fellow. He tried several times to reveal secrets he ought never to have been in possession of. You heard him. Miss Wentworth may have branded him an impostor – whatever she means by that Boy’s Own Paper designation – but he showed a certain depth of knowledge of our services’ operations. Showing off for the prince, of course, but there were other receptive ears in the neighbourhood. It seemed the only way of silencing him. No one believes a word uttered by a man in his cups. Rendering the subject harmless, sir, that’s what I was doing. As no one else seemed about to take it upon himself,’ he added rebelliously. ‘It was hardly believable, the gross behaviour the man exhibited, but he caught sight of Miss Wentworth’s full plate – she had to my notice not attempted so much as a forkful – and began to dig in. He clearly couldn’t resist the red caviar – he started with that.’

Inspector Chappel grimaced. ‘Well, they say that Rasputin of theirs had the table manners of a hog and the appetite of a brown bear. Must be the cold winters that do it.’

‘Not immediately, but several forkfuls later, in mid-sentence, mouth still full of food, he keeled over.’ Rupert pushed on with his account. ‘Choking, red in the face, unable to breathe, clutching his heart. All the symptoms of a heart attack or cyanide poisoning.’

‘And I can confirm the latter. In attempting to resuscitate him, I’m sure I detected a strong scent of almonds on his breath,’ Sandilands said.

‘Sir, one of the dishes – the fricassee of Persian lamb – had almonds amongst its ingredients,’ Lily offered.

‘As well as all the spices of the orient. As good a way as any of disguising the scent of cyanide. I took some of that dish myself. Like many others now snoring peacefully in their beds,’ he added thoughtfully. ‘So – by mistakenly eating from Miss Wentworth’s plate, the Serbian signed his death warrant.’

‘Er … No chance, I suppose, that anyone would be targeting Miss Wentworth herself?’ Chappel asked sheepishly. ‘I know, I know – it sounds ridiculous, but training makes me bring it forward. Purposes of elimination and all that … clear out the underbrush. She was the one who was handed the poisoned plate, after all. Got to consider it!’

‘A reasonable thought, Chappel …’ Rupert Fanshawe allowed, ‘if we must plod every tedious inch of the pedestrian way to the truth. But – and this will come as a surprise to you fellows – Miss Wentworth was not, in fact, the one who was handed the poisoned plate.’

He waited for the astonished stares then carried on, his voice purring with anticipation: ‘And, as long as the spot-light’s on the constable, may I suggest we follow up with a further reasonable thought? We should remind ourselves that what we are seeking in all this is a malign female presence. An unknown woman on assassination bent. Our Morrigan.’ He turned a sweet smile on Lily. ‘Now, Miss Wentworth was the woman closest to the Prince of Wales from beginning to abrupt end and she had continuous access to him. We, gentlemen, had placed our prince in the hands of a stranger for the whole evening. A stranger to him … a stranger to us. Can any one of us claim to know who she is? Where she comes from? Who precisely stands as her guarantor? Oh, I am much to blame. I should have taken immediate action.’ He shook his head to underline his self-recrimination. ‘If only I had acted in accordance with my training and arrested Miss Wentworth the moment it became clear that her behaviour at the buffet was suspicious, we could have avoided a murder.’

‘Eh? What are you on about?’ Lily murmured.

‘Suspicious behaviour? Describe it, Fanshawe.’ Sandilands was peremptory.

Fanshawe enjoyed the incredulity for a moment. ‘I watched as the food was being put out. I watched as Wentworth followed the prince to a table. There she snatched his plate from him and replaced it with her own. Oh, it was neatly done. But the movement was not in the briefing. It exceeded instructions. It was surreptitious and possibly suspect. We were at the ball to prevent a young woman – a young woman with certain social graces – “Mayfair”, I believe, was the Assistant Commissioner’s judgement – from getting close enough to the prince to kill him. And here was one such sitting by his side and forcing the food of her choice on the prince with all the skill of a music-hall card sharp. She could easily have anointed the oysters with something nasty held in her hand. If I’d made a fuss and had both plates taken away at that moment, the poison would have been discovered there and then. And Prince Gustavus would still be alive. You have my unqualified apology, sir.’

Rupert drooped then raised his head in defiance. He swept his floppy blond quiff off his forehead, the better to stun them with his blue eyes ablaze with an emotion which clearly anticipated a coming martyrdom. ‘I’m ready to accept whatever proportion of blame you care to assign to me, sir.’ And he added coldly into the shocked silence: ‘After you’ve chucked the book at Wentworth.’

Lily shivered, devastated by the implications. The two plates had been exactly alike. If Fanshawe had proceeded with the scheme he’d just outlined there was every chance the plates would have been confused on their way to the laboratory. Intentionally or accidentally. Who would ever know? She wouldn’t have been able to distinguish them herself. Both carried her fingerprints and those of the prince. Accusations would have been made. From what they’d stitched together of her background she knew they could make a spectacularly convincing case against her. ‘Left-wing, anti-royalist, worms her way into the Royal Presence …’ Poison was known to be a woman’s choice of weapon.

A pit of horror opened up before her. If they were seeking an easy suspect to cover for their incompetence, she would find herself occupying a cell in Vine Street within the hour. She looked instinctively to the commander for support.

Her appeal went unacknowledged. He was watching Fanshawe, head on one side, quizzical, encouraging him to go further. It occurred to her – and the realization hit her like a thump in the stomach – that for these men, all of whom had a position to lose, the career, the life even, of a lowly woman policeman on the point of leaving the service anyway would count for little. She was expendable. They were officers. Ex-military. It was men of their kind who’d sent out Tommies to die in their thousands on the Somme. She too was no more than cannon fodder.