The exercise, my sense of pride in my achievement and the unseasonal sunshine produced in me a joy that I had until then never known in this incarnation. I practised my greeting to Nicholas for the last ten minutes of the walk home, articulating the words with increasing facility. As soon as he opened the door to me, I held up my plastic bag and announced proudly: ‘Look what I’ve got. Foked smish.’

He glanced nervously over my shoulder and yanked me in.

Nicholas was naked from the waist up. He had something oblong in the palm of his hand.

‘Smoked fish,’ I said.

‘Give me a hand with this,’ he said. ‘It’s time to call Hunter’s bluff. We can’t wait any longer. Misha texted me this morning. He says they’re closing in on us.’

It was a miniature recorder. I held it in the shallow valley of Nicholas’s sternum while he fastened it in place with strips of gaffer tape.

‘I’ve arranged to meet him at Butler’s Wharf. He won’t be able to try anything there. All I need is some acknowledgement from him of what he’s up to. Then we’ll go straight to the police.’

At half past ten, Nicholas spread newspaper on the tiles of the hearth in the sitting room and dislodged the package from the chimney. He wiped it clean and put it in his courier’s bag. He handed me a piece of paper.

‘I need you to memorise these numbers,’ he said. ‘This is mine, this is Misha’s. If anything happens to me, call Misha. But use him sparingly. He’s no use to you dead.’ He paused at the doorway. ‘Wish me luck.’

‘Good luck,’ I said.

He looked at me. We embraced, this time with genuine warmth. No words were necessary. I understood.

The wait recalled those impotent and anxious hours before childbirth, tethered to an outcome over which you have no control, trying to cast all the dark possibilities out of your awareness. You would think that at a moment of such tension, Nicholas’s proxy complex would feel something, some sympathetic vibration at a cellular level, as twins are supposed to. But there was nothing.

Outside, the sky brightened. I drank Lucozade and felt its bubbles prick my tongue.

At just after 3.30 p.m. the mobile phone handset on the coffee table burst into life. It rattled on the glass like a hostile insect. The caller was Misha. ‘Go quickly,’ he said. ‘Go now.’

*

So close to my own death, I’m squeamish about dwelling on Nicholas’s. I’m sentimental about the body that formed me. I’m not blind to its inadequacies and imperfections, but it’s what I was. It’s not merely a platitude to say that something of me died that day. And though I’m not superstitious, I find myself recoiling from the details of Nicholas’s death as from a harbinger of my own. But completeness demands it.

Nicholas’s body was retrieved from the front nearside wheel arch of a lorry that had been turning left from Kennington Park Road onto Harleyford Street at 4.28 p.m. on Monday September 28th 2009.

I avoided using the word ‘mangled’ in the previous sentence, fearing that it would cheapen the tone, but now I find that making no mention of the body’s condition deprives the statement of some of its impact. Perhaps it is enough to ask the reader merely to imagine the likely outcome of such a collision.

The inquest was held in Croydon. I couldn’t risk attending, but I was able to find its details online.

The court heard the testimony of a single witness and the collision investigator, a PC Menzies, whose report gives the appearance of scrupulousness. He described the condition of Nicholas’s bicycle in detail. ‘The front fork, down tubes and pedals were all smashed. A wheel was buckled. Paint was flaked off. There was a long groove in the tarmac where the bicycle had been carried along the ground.’ Using careful legal language for quantifying uncertainty, PC Menzies abrogated any responsibility for explaining what might have happened. ‘There were no defects of note in the driver’s vehicle. The quality of the CCTV is such that it is not possible to determine the speed at which he was driving.’

The driver of the lorry, a Liverpudlian called David Test who was working on a short-term contract to a firm of hauliers called Wexford Dairy Refrigeration, claimed he had checked the nearside mirror twice before the fatal manoeuvre; though not the most clearly false element in his account, there is something about the detail twice that stretches credulity with its unlikely excess of driving punctilio.

According to the coroner, life was pronounced extinct at 4.45 p.m. She recorded a verdict of death by misadventure: ‘… when, just after 4 in the afternoon, amidst a lot of uncertainty, the two came into collision. Nicholas Patrick Slopen, born Singapore, 1970, died of multiple injuries.’

*

It’s not difficult to piece together what really happened. Nietzsche says the liar gives himself away by the shape of his mouth. The story is in the omissions and the minor details as much as the outright untruths.

Leaving aside the strange absence of witnesses on a busy road in South London on a weekday afternoon towards rush hour – with the notable exception of a dubious Serbian called Lenko Voinovic who supported Test’s account in every specific, despite claiming to have been on the phone to Belgrade at the time – and ignoring also the mystifying inadequacy of the traffic cameras in the area, there is a further number of puzzling details that raise questions about the verdict of accidental death, and ultimately about the integrity of the coroner herself, Ms Geraldine Passmore.

More than three hours had passed between Nicholas’s meeting with Hunter and the accident. Three hours is a long time. It wouldn’t take Hunter three hours to say ‘Publish and be damned’ or ‘I don’t have any idea what you’re talking about.’ Three hours, I would say, is just about enough time for Nicholas to have laid out his accusations against Hunter patiently and thoroughly; for him to have overcome all Hunter’s attempts at bluff and appeasement; for Hunter to have become genuinely worried that Nicholas had the goods on him; and for Hunter to have set in train the fatal reprisal.

What had he been doing, or rather, what was being done to him in those three hours? Clearly, it was something of so violent a nature that only the convenient fiction of a traffic accident could plausibly conceal it. Notably, there was no mention of the recording device, the microphone or the dossier which Misha and Nicholas had taken such pains to compile.

*

There was no question of staying in the flat. Nicholas’s death had left me with no doubt about the reach and resourcefulness of the conspirators. I was certain they would come for me next. I left London and submerged myself in the transient world of flotsam and rejects. I travelled by bus between out-of-the-way towns. I stayed in hostels and shelters. I kept moving.

The people I encountered assumed that I had had some kind of stroke and after a while I began to encourage them in this belief. I concocted an autobiography in which the stroke had given me an opportunity to take time away from my career and re-evaluate my life. Adding that I had previously worked as a civil servant was normally enough to forestall any further enquiry. The rehabilitation that had seemed so elusive before, now took place inexorably. Each day, I felt more rooted in my carcass, my mind seemed increasingly alert and my speech became clearer. And once I became more confident of my survival, it began to dawn on me that Nicholas’s sacrifice had not been in vain. Perhaps I could become a sufficiently plausible Nicholas to send a tremor through the Common Task. Perhaps I could sharpen myself into an arrow to pierce the heart of the conspiracy.

Once in a while, I checked through my old email account and in this way learned from a circular sent to all alumni of Downing College that a former girlfriend was running a shop in a market town in the Welsh borders. One morning, I went into her shop unannounced. Of course, there were emotional ties between us. I craved any connection with my old life. But it was also a way of assessing my progress. If she believed I was Nicky Slopen, others might too. I glimpsed a chink of light beneath the door of my prison.