Again, for a moment she was back in this room two years ago, making a similar call. That time she’d taken a unit off Abu Mujahid and diverted them to her father’s old friend’s operation. And that decision, that split-second call, had haunted her every day. A tiny decision, made out of some loyalty to her dad’s memory, had set off the chain of events that led to Abu Mujahid’s escape, Isobel Harris’s death and countless other bloody atrocities – a blood-smeared chain that linked her to the death of Rebecca Gladstone less than an hour ago in her ground-floor flat. Was she right this time? Her gut told her yes. She knew Abu Mujahid inside out, better than anyone. She had studied every file, read every report, chased every lead. But a tiny voice of reason urged caution. The evidence was circumstantial, patchy even. He could have one hundred other plans, or none at all. And what if she was wrong again? Could she live with the humiliation that would follow for her, and for Tennant? And could her career survive another cock-up with Abu Mujahid if he appeared in some Islamist video online in days to come, boasting that he had defeated the Met one more time? She went over to a monitor to study the map of Abu Mujahid’s likely journey.

A minute later, a DC in the CCTV team called out. ‘Think we’ve got him.’ The main image on the video screen flashed to a CCTV camera pointing along Devonshire Street, a broad but quiet road lined with red-brick office blocks, clad at street level with bleached Portland stone. A man scurried along with a small rucksack slung over his shoulder, and an anorak hood pulled over his head.

‘He’s heading east, ma’am, in the direction of St Pancras,’ said the young DC. Again, Gabriel felt a swell of euphoria. Was this how riders felt in the old days of legal fox hunting, when the scent of their quarry was in the nostrils of the hounds? They watched further. The figure stopped and for a moment his profile was frozen on the screen. It was a teenager, aged sixteen or seventeen.

‘False alarm,’ said the DC, unnecessarily. Gabriel felt a pang of frustration.

‘He’ll be at the station in fifteen minutes. Who’s gone down there to brief the spotters?’

‘DI Skeffington, ma’am,’ said Bose.

Gabriel failed to mask her dismay. ‘And whose idea was that?’

‘He volunteered, ma’am.’

‘Shit.’ She took a deep breath. Skeffington was the worst choice. He’d barely hidden his contempt for Gabriel since the start of the hunt for Abu Mujahid. She could not think of a less suitable candidate for this job.

She made up her mind in an instant. ‘Listen, Eva, I’m going down there to join him.’

‘Ma’am?’ Bose was incredulous. She followed Gabriel, one step behind her as she grabbed her coat, swung her bag over her shoulder and made for the stairs.

‘Sod it, Eva, you know it makes sense.’ They’d reached the first floor by now, the clattering of their feet echoing up the stairwell, Bose panting as she struggled to keep up. ‘I don’t have to tell you what I think of Skeffington. And no one, absolutely no one, knows Abu Mujahid better than me. I want the spotters energised – not sent off half-cocked because the briefing officer would rather be in the bar.’