‘If you say “… making a valuable contribution” I will not be held responsible for my actions.’

‘I was going to say “making a difference”,’ she said. ‘You could always go to the states, I bet the FBI would have you.’

‘Why would the FBI have me?’ I asked.

‘They could use you as an Obama decoy,’ she said.

‘For that,’ I said, ‘you can pay for the kebabs.’

In the end we were too knackered to get kebabs, so we headed straight back to the section house where Lesley utterly failed to invite me to her room. I was at that stage of drunk where you lie on your bed in the dark and the room goes whirling around you, and you’re wondering about the nature of the universe and whether you can get to the sink before you throw up.

Tomorrow was my last day off, and unless I could prove that seeing things that weren’t there was a vital skill for the modern police officer, it was hello Case Progression Unit for me.

‘I’m sorry about last night,’ said Lesley.

Neither of us could face the horrors of the kitchenette that morning, so we found shelter in the station canteen. Despite the fact that the catering staff were a mixture of compact Polish women and skinny Somali men, a strange kind of institutional inertia meant that the food was classic English greasy spoon, the coffee was bad and the tea was hot, sweet and came in mugs. Lesley was having a full English breakfast; I was having a tea.

‘It’s all right,’ I said. ‘Your loss, not mine.’

‘Not that,’ said Lesley, and smacked me on the hand with the flat of her knife. ‘What I said about you being a copper.’

‘Don’t worry,’ I said. ‘I’ve taken your feedback on board, and having extensively workshopped it this morning I now feel that I can pursue my core career-development goals in a diligent, proactive but, above all, creative manner.’

‘What are you planning to do?’

‘I’m going to hack HOLMES to see if my ghost was right,’ I said.

*

Every police station in the country has at least one HOLMES suite. This is the Home Office Large Major Enquiry System, which allows computer-illiterate coppers to join the late twentieth century. Getting them to join the twenty-first century would be too much to ask for.

Everything related to a major investigation is kept on the system, allowing detectives to cross-reference data and avoid the kind of cock-up that made the hunt for the Yorkshire Ripper such an exemplary operation. The replacement to the old system was due to be called SHERLOCK, but nobody could find the words to make the acronym work so they called it HOLMES 2.