‘Be careful, sir,’ Tiana said.

Zayan Lal looked comfortable and balanced and, glancing to his left, ran nimbly up and over the apex of the roof, barely using his hands for support. Gillard, attempting to do the same, slipped on the damp moss, and only saved himself by grabbing the ornate knurl of a ridge tile. Peering over the edge to the other side, he saw Lal below the level of the guttering, arms busy, seemingly working away at the catch on a mullioned window. The scratching noise indicated he had found a use for his knife.

The detective scrambled back down, and into the door he had come from. With a finger to his lips to ensure Tiana’s silence, he indicated the other side of the building. They waited in an alcove, listening as the fugitive continued to work away at the lock of a corridor window. Finally, they heard the casement open, and the light thump of two athletic feet hitting carpet. Two seconds later the detectives jumped out. Lal was in a short corridor that ended in a padlocked door. The only way out was through Gillard and Tiana, or back out of the window. He tried the latter, one foot on the sill, but Tiana was on him immediately, seizing the trailing leg. As she pulled him to the carpet, he spun around, the knife arcing towards her neck. Gillard fell on Lal like a ton of bricks, knee in the midriff, both hands on the knife arm. In thirty seconds it was all over.

DCI Gillard and DI Claire Mulholland looked through at the CCTV into the cell where Zayan Lal was sprawled on the blue plastic bedding, arms behind his head, feet on the wall. Gillard knew from decades of experience that this was the behaviour of the guilty. It was the innocent, the bewildered, those who didn’t know why they had been arrested, who had the nervous tics, who paced around, and who wept. In many cases, those who knew they had committed crimes were relieved to finally have been caught. The tension was lifted. It was no longer down to their own judgements or decisions. Justice would take its course.

Getting Lal to that catharsis, where he was happy to confess, wasn’t going to be straightforward. Although Gillard was eager to interview the man, he knew it was better to get all available evidence first. They could get him easily for dealing cocaine, forty grams of evidence was right there in his apartment. But there was nothing other than circumstantial evidence for the poisonings and the assault on Mrs Roy. The CPS had been quite clear. The cross-contamination of Jason Waddington and Mrs Roy’s forensic samples and the connection between Kirsty Mockett and Deepak Tripathi were both gifts to the defence team. If there was even a suspicion that Kirsty had taken money from Tripathi to tamper with evidence, then her valuable witness statement about the cyclist and anything she had access to at the crime scene, or during the search of Mrs Roy’s flat, would all have to be set aside. Ideally, Gillard needed fresh evidence that didn’t rely on any of the forensic work that had been done so far. That was a huge ask. But the first place to look for it was in Zayan Lal’s apartment.