She had resisted the urge to release his picture to the media. Maybe in a day or two, but now she wanted to find him and follow him in the hope he would lead them to the next NRF target.

The photofit from the interview with the Iranian journalist smuggled into the UK had come through. Like many of these images, it was next to useless. She stared at the long face and hard eyes. The red hair was a good match for Abu Mujahid, and the beard fitted the most recent description. ‘Is that you?’ she asked the picture on the screen. Did she have enough to push this line further – and maybe raise it with Tennant?

By lunchtime, she sensed she was becoming unreasonably irritable, but lacked the urge to restrain herself. She had snapped at Bose, bitten the head off a DC and felt herself close to thumping Skeffington. This was no good, she thought, she needed to stretch her legs, clear her head.

She emerged into an oppressive winter fog. There’s nothing romantic about city fog, she thought sourly as she walked towards her favourite sandwich shop opposite St Pancras, unable to see more than a few metres in front of her. It was a bloody nuisance. Her phone rang.

‘Ma’am.’ It was Skeffington. ‘Report from the surveillance team outside Rod Houghton’s house. Guess who’s just walked through his front door.’

#

New Scotland Yard, Victoria Embankment, London

Gabriel waited in the poky conference room overlooking the Thames and watched the stream of cyclists on Victoria Embankment below. Even on a misty winter day, the cycle lane was congested with rental bikes and Lycra-clad commuters.

Tennant came in and sat opposite. Do I look that knackered too, wondered Gabriel as she studied his washed-out complexion and the battleship-grey creases under his eyes.

‘Excellent work on Rod Houghton,’ said Tennant. ‘What now? We’ve got the DNA match – haul him in or let him run?’

‘Think we keep him out, sir,’ said Gabriel. ‘We’ve got nothing on the third NRF attack, we’ve got nothing on the location of Douglas Glenister, his conspirator. If we bring him in, we tip off the NRF and they’ll change their plans or bring forward the next attack.’

‘But he’s canny. He’s special ops. There’s a risk we’ll lose him.’

‘We just have to make sure we don’t. It’s the least imperfect of two imperfect options.’

Tennant mulled it over. ‘Do it. Twenty-four hour surveillance, and the full monty – tap his phones, wire up his car. I want a full account of every time he goes to the toilet. What about trigger plans?’

‘We’ll pull him in if he visits the high-risk locations – ports, airports, the usual,’ said Gabriel. ‘And if we get wind that he has access to weapons.’

‘The Home Secretary’s office is constantly on the phone, but I’ll keep the politicians out of the loop for a day or two while we work out the strategy,’ said Tennant. ‘Nothing more on this associate of his, Douglas Glenister?’