‘Hold your horses,’ Gillard said, and pressed four bells for second-floor flats. Leaning his head in to the intercom, he waited for someone to answer. A woman did, and he apologised for waking her. ‘It’s the police, would you kindly buzz us in?’

‘Is it about the dog fouling?’ she asked.

‘No, madam. Please, just press the button.’ She did.

The entourage clomped in, and gathered around the two lift entrances. When the lifts arrived, Gillard went with the crew to tackle Harry Roy on the eleventh floor, while Platt headed to the tenth, under instructions not to ram the door without asking him first. ‘That occupant is likely to be in the higher flat. So wait for my say-so.’

Outside Harry Roy’s door, the detective rang the bell, while ten-ton Tony Tunnicliffe, as he was known, hammered on the door with his fist, bellowing, ‘Police, open up.’ They waited five seconds, and Tunnicliffe began again, making a huge racket. The door opened as far as the chain allowed, and Gillard saw Harry Roy’s shocked face, with a toothbrush sticking out of it, and a silk dressing gown below.

‘What on earth is the matter?’ he said, foamy toothpaste down his chin.

‘Open it NOW,’ Tunnicliffe yelled, blocking out Gillard’s attempt to make himself heard.

‘Harry, I have a search warrant,’ the detective repeated, showing him the document. ‘Is Zayan Lal in there with you?’

‘Open it NOW,’ Tunnicliffe repeated. ‘Or I’ll smash it down.’

Gillard lifted a restraining arm in front of Tunnicliffe, leaving Harry time to close the door and unchain it. The officers barged in immediately, and fanned out across the luxury flat.

‘Where is Zayan?’ Gillard asked.

‘He’s not here,’ Harry said, with just enough of a hesitation to show he was lying. The detective saw movement, a hem of curtain billowing. Gillard raced past Harry, threw the drape back and discovered the sliding door to the balcony was partially open. He went through into a lash of rain and wind, and saw to his left Zayan Lal, crouched on top of the left-hand edge of the terrace handrail, perfectly balanced, just one hand reaching down steadying himself. The pose was familiar somehow. Gillard remembered, from a film poster. Spiderman, poised to jump.

‘Don’t!’ Gillard said. ‘We just want to talk to you.’

Zayan glanced at the detective and then below at the drop behind him. It was a long, long way down. Eleven stories to a concrete path, formal gardens, then, thirty yards further out, the river. The lazy Thames, winding its way towards London, with a long history of ferrying the dead and dying.

‘Don’t do anything stupid.’ Gillard edged closer, the rain lashing his face.

‘Then stay away.’ Zayan was wearing tracksuit bottoms, a white T-shirt, and training shoes. His muscled forearm readjusted its grip on the stainless steel rail, fingers moving as if fidgety for flight. Gillard had never before noticed his athletic poise. He turned back to the detective.

‘Leave Harry out of it, Gillard. He doesn’t use.’