‘I’m here about murder, not drugs.’

‘Then you’re wasting your time.’ Zayan glanced behind him, again considering the drop.

‘Why did you kill her, Zayan?’

‘I didn’t. It wasn’t me.’

Behind Gillard, the glass door slid further open, and Tunnicliffe’s bulk muscled out. The stainless steel terrace, for all its generous proportions, seem to flex. Out here, two was company, three definitely a crowd. ‘I’ll get him,’ the big cop said and, before Gillard could stop him, he lunged.

Zayan fired himself backwards from the balustrade, as if spring-loaded. He twisted away from Tunnicliffe’s grasping paws, and then fell, disappearing in a moment. The big cop banged into the rail, half over the edge of the rail himself, and it took all Gillard’s strength to stop him from tipping over the edge. By the time the detective peered over, Zayan was gone. There was no body on the grass, no corpse on the concrete. The Thames, impassive as ever, seemed undisturbed.

‘Where the fuck has he gone?’ he whispered.

Tunnicliffe, on his knees and winded, croaked out something.

‘What?’

‘On the other balcony. He landed—’ the rest was lost in a coughing fit.

Gillard stared over the edge. But Zayan wasn’t on the terrace on the floor below. It was at least twenty feet down, and there was a fifteen-foot void to cross to get there. He turned back to Tunnicliffe. ‘He’s not there.’ Then he looked again. There were all-weather cushions on the other balcony, and in the middle of one, a series of dirty, newly-wet footprints.

‘Fuck, that’s his own flat.’ Gillard grabbed the big cop’s radio, and called the rest of the team. ‘Get into the tenth floor flat, I want someone on the ground floor too. Don’t let him get away.’

There was a crackle of static, then an acknowledgement.

Before Gillard had finished, Harry Roy burst out onto the balcony. ‘Zayan?’ He was still in a dressing gown, still with toothpaste smeared down his chin.

‘He jumped,’ said Tunnicliffe, inclining his head towards the parapet.

Harry let out an anguished shriek and rushed to the guardrail. Gillard grabbed him by the shoulders and said: ‘It’s all right, he landed on his own balcony. He’s inside his own flat.’ He wished he knew that for a fact.

There was a noise across and below from the other balcony, and a cop in a stab vest burst out, looking confused.

‘Have you got him?’ Gillard yelled.

‘No, sir. He’s not here.’

‘He must be. Search the flat.’

‘We are, guv, don’t worry.’ He went back inside.

‘Don’t let him get away, you idiots,’ Gillard muttered. He left Harry Roy in the custody of PC Tunnicliffe, and raced back through the flat, past the dining table on which laptops phones and tablets were bagged up, ready to be removed. He ran out of the flat through the corridor to the fire escape opposite, pounded down one floor of the concrete stairwell and burst out into the hall below where, from the noise it sounded like, Zayan Lal’s flat was being demolished. A small gaggle of residents gathered round the PC at the ram-damaged doorway, asking questions and getting nowhere. They turned to Gillard as he approached.