Robin grinned at me. ‘If you want to bag a tiger you need the right equipment. You need a whole new set of clothes, bank account, the works. We need to create a package your targets cannot resist.’

‘Ready when you are,’ I replied, with a fierce thrill of excitement.

‘First, we’ll have to install you in a rented flat.’

And that was how I came to be sharing a flat in South London with another UC officer, but she was never there as she had her own ‘other’ life. Then for four months Robin and I painstakingly constructed my alibi and cover story.

‘We usually use our real Christian names,’ he said. ‘If someone from your old school recognizes you from across the street the hope is that they will simply call out your Christian name.’

I nodded, but I had pushed all my friends away after Luke died.

‘Do you have a name you’d like to assume?’

‘Hart,’ I said immediately. ‘Lily Hart.’

‘Right, time to apply for a passport dating from three years back and a driving license.’

‘Why would a runaway have a passport?’

‘Because she toyed with the idea of dancing in Amsterdam?’

They arrived in less than a week. Both fake passport and DVLA issued driving license had been created in collusion with the appropriate governmental departments and were good for travel and if I was stopped by the police. Using those, I opened bank accounts and applied for credit cards.

Robin took me to lap dancing clubs so I could watch the girls, the way they behaved, and how they interacted with their customers. I saw them rub their naked flesh against men and I thought I had cringed inwardly, but Robin must have sensed my discomfort.

‘The most important thing I learned, first and foremost,’ he said quietly, ‘was that whatever I was doing, I had to always remember that I was a police officer.’

I turned to him. His face was unusually serious.

‘Don’t allow yourself to get psychologically mixed up. Always keep what you are doing and who you are separate. At the end of the operation you will ditch all the physical trappings of your undercover alter ego, the hair, the clothes, the people you have befriended, and return to your own normal world.’

‘Is that really possible?’ I asked, surprised.

He looked me in the eye. ‘You have to. If you don’t maintain the line between the job and who you really are you will become a wreck. For example, if you find yourself in a position where you have to take a drug then you have to come out of that personality as soon as possible and tell your handler, in your case DS Mills. And if necessary you will have to go for counseling.’

‘Will I have to take drugs?’ I asked worriedly.

‘No, we will put it into your cover story that you’ve had a very bad experience, nearly died, et cetera, and no longer touch the stuff.’

‘When and how do I start asking for information?’

‘Work your way in very slowly,’ Robin said. ‘This is a long-term assignment and so requires a huge element of deception. We don’t want the target to get suspicious. He is very intelligent, wary, and uncommonly aloof. Don’t appear too eager for information. In fact, don’t ask for any information. Let some chances to ask for information go by. Don’t even appear curious. Lull him into a place of complete trust before you sink the hooks in.’

He then warned me that constant fear of discovery and letting the side down, which was part and parcel of undercover work, could manifest itself as sexual arousal. ‘Watch for it and be prepared for it.’

That night he also introduced me to Anna.

Over the next two months she gave me pole-dancing lessons and taught me some really cool moves that looked good and professional, but didn’t take an athlete to perform.

A week before I was due to start my assignment I had my nails done and glamorous red highlights put into my hair. I looked into the mirror. There. My alter ego was ready to be unleashed.

On the day before I was due to meet Patrick, who would take me on my audition at Eden, I went to see my parents. We had dinner together at a restaurant. The hole that was Luke was bigger than ever. My father told me he was very proud of me.

‘When will you come to see us?’ my mother said, crying quietly.

‘I don’t know, but I will call.’ The reality was I wanted my new life to begin. I wanted to stop being Lily Strom and begin my new existence as Lily Hart.

I had become quite close to Robin and on that morning before I left to start my assignment he hugged me. His parting words were, ‘Never let your guard down. Remember, one false move can give you away.’

But what stayed in my mind and haunted me was what he had once told me when we were dining at a Chinese restaurant. He told me the loneliest place in the world was the place inhabited by the undercover police officer when they are deep inside the mind of a fictional person.