By noon Gillard, Claire Mulholland and two uniforms were back outside Lal’s tenth floor Walton-on-Thames apartment. The corridor looked like the site of a medieval siege. The smart hardwood door, taken right off its hinges by the police ram, had been roughly fixed back, held on with four hasps and padlocks. The corridor carpet was stained and gouged, presumably where someone had dropped the ram after use. There had been several complaints by Lal’s neighbours about the heavy-handedness of the police raid.

One of the PCs unlocked the padlocks and manoeuvred the door open, allowing the two detectives, wearing latex gloves and polythene overshoes, to go inside. The raid and hurried search had done a tremendous job of wrecking the integrity of this flat as a potential crime scene. CSI chief, Yaz Quoroshi, had taken a quick look on the day of the raid, and was scathing in his report about the chances of finding undisturbed forensic evidence. Nonetheless, his team had produced a series of photographs which Claire now had in her hand. Yellow markers in the flat and the pictures showed where Lal’s mobile phone and other devices had been found, and the cocaine stored within several DVD boxes.

The two-bedroom apartment had once been tastefully decorated. The least disturbed room was the kitchen. ‘I’m surprised that the plods didn’t search here more carefully,’ Gillard said to Claire, as he picked his way through the many spices and herbs. ‘The man began his career at Empire of Spice as a demo cook.’

‘So it was probably in here that he made his preparations of thallium and glycol.’

‘Thallium, yes. Probably not glycol, as he left here days before turning up at our canteen. My guess is the glycol was an opportunistic event. Besides, CSI already swabbed the surfaces here, and didn’t come up with anything.’

One of Gillard’s instructions to CSI had been to look for a matching chrome-coated hand weight to that used to kill Mrs Roy. These things were used in pairs. CSI had found nothing in this flat, nor in Harry’s penthouse, nor even in Morag Fairburn’s house. The gym that Harry and Zayan were registered to likewise had only much more modern weights. Probably Lal had ditched it soon after the attack. ‘Where else, near at hand, could Zayan Lal have dumped incriminating stuff, do you think?’ Gillard asked.

‘Up on the roof, or in the maintenance areas?’ Claire suggested.

Gillard inclined his head in acknowledgement of this thought, and then clicked his fingers as a fresh idea came to him. ‘Aha! There is a much safer place. Follow me.’

Gillard led Claire out to the front doorway, towards the fire escape, and then down one floor. They took off their booties and gloves. ‘It’s here that I saw Lal’s muddy footprints, leaving this apartment. He had climbed down from his own balcony just above. Harry said that Zayan had a key to the terrace door here.’

‘How come?’

‘He used to walk the woman’s Yorkshire terrier, and sometimes let the cat out onto the terrace where its litter tray was, according to Harry. That’s how he managed to give us the slip.’ Gillard pressed the doorbell and after a minute of yapping from within, the door was opened as far as the chain would permit. A woman in her eighties eyed them dubiously even after they had explained who they were, but unlocked the door and let them in.