“Indeed, he could not. You see, this is not Frank, but his identical twin-brother, Sean Delaney. The same man who has now assumed control over the Delaney Gang and made such an enemy of Edwin Halvergate.”

The mention of Halvergate’s name brought a sharp response from the injured Sean Delaney. “He’s the man you really ought to be locking up, Walcott. I don’t know who these gentlemen are, but they seem to have outfoxed us this evening.” He then looked directly at Holmes with an expression of pure hatred. “My friends will ensure that I escape the noose. Be certain of that. But as a gang we are finished. Halvergate has already begun to target my men and disrupt all of our operations. He even had my own father in his pocket.”

Inspector Walcott was quick to defend his former colleague. “Your father had more sense than to challenge Halvergate and you placed him in an impossible position. He acted only to stop you being killed and you reacted by taking his life. Something you will have to live with, and explain to your younger twin-brother.”

Delaney looked down and grimaced as he pulled his wrist to his chest. He had nothing further to say.

We accompanied the men down to the foyer and thanked the doorman for his earlier assistance. While Holmes and I kept guard over the pair, Inspector Walcott went off to despatch a telegram to the police station. Fifteen minutes later a squad of four uniformed constables arrived with handcuffs and led the gang members away.

Before his departure, Walcott could not resist asking Holmes a final question. “Mr Holmes, Dr Watson. I am forever indebted to both of you for your assistance today. That you have achieved so much in such a short space of time is truly beyond me. But I am intrigued to know how you could be so certain that Sean Delaney and, indeed, Thomas Logan, would come to the hotel room, rather than any other members of the gang.”

Holmes eyes were wide with delight. “My dear Inspector. Sean Delaney has staged a recent takeover within the gang. He may have assumed control, but would not have trusted anyone other than those close to him. As the man in jeopardy was his own brother, it seemed fair to assume that he would wish to be involved, accompanied by the ever-present Logan. Delaney is a man who leads from the front, something that has now signalled a death knell for the family in this city.”

“So it would seem,” I added, shaking Walcott warmly by the hand. We said our goodbyes and watched as the dogged, but weary, inspector left the hotel.

The next morning, Holmes and I were up bright and early to catch one of the first trains back to London. It was almost midday when we arrived back at Baker Street. Mrs Hudson greeted us at the door, looking relieved that we had returned in good health following our impromptu departure the evening before. A short while later we were sat comfortably in front of a crackling fire enjoying some tea and buttered crumpets.

When Mrs Hudson came to retrieve our plates and cups, she carried with her a small parcel. “I forgot to mention it earlier, Mr Holmes, but this arrived for you about ten o’clock this morning.” She handed him the parcel and proceeded to clear away the crockery.

Instinctively, Holmes began to examine the packaging and even before he had unwrapped it announced, “Curious, Watson. This is from Edwin Halvergate. Let’s see what it contains.” He removed the brown paper covering to reveal a small book and flicked through the first few pages. “Mr Halvergate certainly loves his poetry. This is a second volume of haiku verse, this one written exclusively by our man. And how touching, he has dedicated it to me.”

I could tell that Holmes’ sarcasm masked a genuine concern. “What does it say?” I asked.

“A single line - ‘Thank you for your recent help at the Grand Hotel - EH’. He is well informed, Watson. And no doubt it will not be the last time we hear from Edwin Halvergate.” With that he placed the book upon the mantelpiece and refused to discuss the matter further.

I left Holmes a short while later, picking up my overnight case from the hallway and saying goodbye to Mrs Hudson. The weather had taken a distinct turn and a dark, mackerel-coloured sky announced that heavy storm clouds were on their way. As I stood awaiting the arrival of a carriage, I glanced back at the upstairs window. And in that moment I realised, that however many criminals, swindlers, thieves and fraudsters we managed to outwit, there would always be another lurking in the shadows, waiting to strike. I shivered at the thought.

4. The Case of the Cuneiform Suicide Note

It was towards the end of July 1903 that I returned from a short break in Ireland; a trip occasioned by the death of a close medical colleague who had established a successful medical practice in Cork some ten years earlier. Relieved to be home, I paid the cab driver and dropped my heavy bags and cases in the hallway. A quick tour of the house suggested that everything was as I had left it, and satisfied that my sanctuary was still secure and free from leaks, wind damage and insect infestations, I took a seat in the front parlour to catch my breath. Scarcely had I time to sit back on the comfortable bergère when my repose was cut short by a loud and distinctive rap on the front door. It was clear that my colleague had timed his visit to perfection.

When I opened the door, Sherlock Holmes stood before me in a fashionable tweed suit and wide blue necktie. He gave me a broad grin and tipped the peak of his deerstalker with the top of a thin walking stick. “Welcome back, Watson. Or, should I say, ‘a top o’ the mornin’ to ya’?”

“Holmes, you must be very well informed about my comings and goings, for I have only just this minute returned.”

The smile did not diminish. “Truth be told, my friend, I had completely forgotten when you were due back and wrongly believed you had made the crossing from Ireland yesterday. You must therefore forgive the intrusion, but I just wanted to be sure that you were still free to come with me this evening to the Library of the British Museum.”

Never one to hide an indiscretion, I felt it best to acknowledge that I had absolutely no recollection of any such appointment.

“Tut, tut, old man, it seems that I am not the only one prone to periodic memory loss,” Holmes retorted. “A little over a month ago, I mentioned to you that Dr Henry Canham-Page, the celebrated archaeologist, was due to give a lecture on the subject of the Cuneiform Records of Mesopotamia and you readily agreed that we ought to attend. His talk is at seven o’clock this evening. If you do still wish to come along, I can call for you at six-thirty.”

Feeling somewhat embarrassed at my faux pas, I acquiesced and said that I would be pleased to accompany him. With a distinct spring in his step, Holmes then turned and headed off with a cheery, “Farewell then, Doctor - until this evening.”

When the hansom arrived at the agreed time I was hovering on the doorstep, loath to keep Holmes waiting and knowing full well how much he liked to get front row seats at any academic lecture so as not to be disturbed or distracted by others in the audience. After a brief ride, we pulled up to the venue in good time and with just a short queue outside were ushered into the British Museum Reading Room with ten minutes to spare.

The reading room provided the perfect setting for the lecture. Situated in the centre of the building, it had an impressive domed ceiling some 140 feet in diameter, modelled, we were told, on the great Pantheon of Rome. And all around us were book stacks, providing over twenty-four miles of shelving for the hundreds of thousands of books housed in the library. It was therefore with some anticipation that we settled down only a few feet from the small raised stage, blackboard and lectern and awaited the arrival of Dr Henry Canham-Page.