I cannot deny I was grateful when a pleasing thud on the doorstep of our comfortable suite of rooms in Baker Street caused my friend Sherlock Holmes to look up from his melancholy scrapings on the violin. 

Our landlady Mrs Hudson descended the seventeen steps to the hall and returned clutching a brown paper package which she handed to Holmes. 

‘What’s this, Watson?’ Holmes said. He must have been befuddled because he knocked over a tray of syringes. I could see that his usually sharp eyes were clouded with the effects of his favoured ‘seven percent solution’ of cocaine. But it never takes him long to snap out