She was a small, fair-haired woman in glasses, neither young nor old, and if you saw her on the train you would not think that she was one of the most experienced homicide detectives in London. I would not speak again until she spoke to me first, for these were the crucial minutes when the Senior Investigating Officer takes a look at the pristine scene, the body exactly where it had been found, letting it all sink in, learning what she can before we start filming, photographing and bagging evidence. Those last moments when the scene is untouched.

Even the blue lights of our response vehicles seemed very distant, as though they were waiting for a sign from the SIO; a large circle of blue lights in the darkness of the massive park, sealing us off from the outside world. I could see DC Edie Wren and TDC Billy Greene interviewing the Romanian men who had discovered the body while preparing for an illegal barbecue.

‘OK,’ Whitestone said. ‘I’ve seen enough.’

I raised a hand to the Crime Scene Manager and on her word the CSIs moved. I saw that our POLICE DO NOT CROSS tape now ran down the length of Park Lane and was patrolled every twenty metres or so by uniformed officers.

‘You’ve locked down all of Hyde Park?’ I said.

‘Because I can always bring the perimeter in later,’ Whitestone said quietly, her eyes not leaving the body. ‘But I can’t extend it later. Better to make the crime scene too big than too small. Let’s take a closer look.’

We wore blue nitrile gloves and white face masks and under the plastic baggies over our shoes we stood on forensic stepping plates that were invisible to the naked eye.

Whitestone and I both carried a small stack of the stepping plates – transparent, lightweight – and we carefully placed them on the grass before us as we created an uncontaminated pathway to the body. We crouched down either side of Mahmud Irani.

‘First hanging?’ Whitestone said.

I nodded.

She pointed with a gloved index finger at the livid, lopsided markings around his neck.

‘You only get that mark from hanging,’ she said. ‘Any other ligature strangulation will leave horizontal marks.’

‘But this is diagonal,’ I said. ‘It runs from low on the neck on one side to just below the ear on the other.’

Whitestone nodded.