After nearly half an hour of following the car from a safe distance, I arrive at a backstreet behind Tottenham Court Road and the driver pulls over abruptly outside a building painted a crumbling, sickly pink.
Driving past the car and pulling up slowly several metres along, I watch in my rear-view mirror. For a moment the BMW is still, and then a side door slowly opens and a pair of pale, bare legs appear from the passenger door, followed by another. A second later the driver emerges too, and the door slams shut.
Again, the man looks around, as if sensing he is being watched. Pushing myself lower in the seat, I follow him in the rear-view mirror, as he beckons the girls with a gesture of his head towards the back door of one of the buildings.
Once the door closes, I find myself staring out onto an empty pavement. Despite being in the middle of central London, the backstreet is quiet, lined with terraced houses on one side and a couple of warehouse-type buildings on the other, including the one into which the passengers from the BMW have disappeared.
For a moment, I am stumped. I can hardly go and knock on the door, and yet I can’t simply sit here. Just as I am about to open the car door, I see movement once more in the wing mirror: the same man, followed by a different girl this time, emerging from the front of the building.
Ducking down out of sight, I watch the girl follow him, blank-faced, into the car. Seconds later, the engine starts up and the vehicle screeches down the street straight past me.
For a second I think about heading after them, but something stops me: a familiar figure moves into view – the bright red cap and post-bag flashing in my line of sight as he turns into the building next to the one from which the man and woman recently emerged, pulling his trolley behind him.
Without a moment’s thought, I push open the door and walk briskly, trying to look casual, meeting the postman’s eye just at the point where he reaches the large black door. Pretending to search in my bag for a pair of keys, I smile.
‘Oh, thanks,’ I say, glancing gratefully at the letters in his hand.
For a fraction of a second I think he will bypass my extended hand, but then, with a glance, he hands me two envelopes.
My heartbeat starts to quicken as he moves away and I am left standing there holding someone else’s post, busying myself with my bag as if rooting around for keys, praying no one opens the door in front of me.
Waiting until he has disappeared from view, I finally dare to look down at the envelopes in my hands.
Pulling my black leather jacket tight around my waist, I stuff the letters into my bag and stare up at the faceless black door, the single bell with an intercom and the tiny camera pointing at the entrance. If the CCTV camera is on, then it’s too late to avoid its gaze. And if someone is monitoring it, they’ve had plenty of time to notice me and come out and ask me what I want.
As far as I can tell, I am alone. Besides, I am too close to turn and leave now.
There is a side gate to the right of the building, partially concealed by black wheelie bins. Walking towards it, I try my hand on the gate, but it doesn’t budge. If I can push one of the bins close enough, I think, assessing the tall spiked gates and the wall embedded with cut glass running parallel to the house down a narrow alleyway, I could easily jump straight over.
At that moment, a sound cuts through the air like a grenade and instinctively I fall to my knees, crawling behind the bins as I hear it again.
At first, it is impossible to know from which direction the voices come. There is a man and woman, that much I can tell; the gravelly depth of his voice and the strained plea in hers makes my blood run cold, the memory of the Heath flashing into focus. Just then another man’s voice rises above them both and the girl goes quiet. For a few moments more, the men continue with raised voices, and yet it is impossible to understand what they are saying.
In a moment of inspiration, I reach into my pocket for my phone – if I record their words, I can ask Mansfield to translate. But as my hand feels inside my bag, I remember my phone is nestling in the footwell of the car where I felt it drop when I took a sharp turn in pursuit of the BMW.
Feeling a pricking sensation on my skin, I keep my eyes squeezed closed, as if this will somehow allow me to protect myself from whatever situation is about to unfold.
But then the sound changes, morphing into an unmistakable grunting before the girl cries out. A sick feeling settles in my stomach and I feel myself frozen to the spot, the sound getting louder and louder until one of the men makes a long groaning noise followed by a brief silence.
Finally understanding where the noise is coming from, I lift myself up slightly and shuffle along on my knees, peering through a tiny gap between the wall and the back door. Pressing my eyes against the gap, I see an open window at the side of the building. Through it, I can just make out a mattress in the middle of the room, a camera set up at the side. The girl is sprawled across the bed, the men either side.
Before another second passes, I scramble to my feet. Moving as fast as I can back to the car, my fingers fumble with the key in the lock. Placing my foot firmly on the accelerator, I feel my heart beating in my mouth as I race through the traffic lights, towards home.