He stepped away, presumably to request reinforcements. Holmes flashed me a small smile.

Lestrade returned, and Holmes continued. ‘Consider these facts. Someone went to a great deal of trouble to disguise the identity of the body. That man was soaked, painted perhaps in some kind of highly flammable liquid or gel. All identifiers including clothes and facial features would be destroyed. Of course, they wanted everyone to think it was Borelli, and so they selected someone of a similar stature. Planted the buckles and the ring.’

‘But,’ said Lestrade, rubbing his chin, ‘how did they get this “other person” into the cauldron? And who is he?’

‘Borelli entered the cauldron and then immediately exited the back, as usual. Fricano, who was complicit, lied about that. I believe you will discover the corpse is that of a man named Santo Colangelo. Presumably he was drugged and covered in this chemical, then loaded in. The back hatch, which usually opened easily, was then secured with the newly added latch. The front as well.’

‘Then he was unconscious, or he would have struggled. But screams were heard.’

‘Colangelo must have come to at some point. Oh, and some kind of kindling substance, highly flammable, was added. That caused the “foof” described to us. And, sadly, the demise of the poor young lady.’ He squinted. ‘Powdered magnesium and potassium chlorate would be my guess.’

‘What is that?’

‘Quite a new thing. “Blitzlicht” it is called. It is used by photographers. You have, no doubt, been temporarily blinded when you were captured by a camera in service of the newspaper men?’

Madame Borelli moaned slightly at the thought.

Lestrade was still not convinced. ‘Who added the latch – er, the latches – then, if not this clever woman?’

‘Fricano, or Borelli himself. Both have the skills. And while Madame was on her errand earlier today, he worked very quickly to pack the bare minimum of his own things – his favourites, no doubt – and replace them with cheap substitutes to make you think he had never left. He and his accomplice, for it must have taken at least two to manage all of this, drugged the lady and set her here in the manner you found her.’

‘Yes, and I do not even drink the gin,’ offered Madame.

‘Applied to your lips, Madame Borelli,’ said Holmes.

‘Then what, Holmes?’ said Lestrade.

‘The act proceeded as normal, with the newly trained assistant, poor Miss Durgen, none the wiser. She lit the match and dropped it in, sealing both Colangelo’s fate and her own. Perhaps more flash powder than was needed had been introduced and that killed her. I doubt that she was an intended victim.’

Lestrade hesitated. No one likes to be topped, even by Sherlock Holmes. ‘Plausible, Mr Holmes, but I am not convinced the corpse is not Borelli’s,’ said he. ‘The body is the same size; it has been confirmed.’