‘Look,’ he said, ‘I think we’re getting distracted by the prepare element here. That’s the job of the police. Ours is to focus on the pursue element and right now the clock is ticking.’ He bent over a keyboard, typed in some figures and up came a road map on the wall screen behind him. It showed all the possible routes between Essex and central London.

‘Right, let’s break this down,’ he said, picking up a laser penlight. ‘On a normal day, avoiding rush hour, the fastest journey time by road from Braintree to King’s Cross takes an hour and ten minutes, give or take. That’s using the most obvious route: the A120 from Bishop’s Stortford.’ He shone the green laser to indicate the Essex town on the screen. ‘Then the M11 gets you into London from the north-east.’ He stopped and wagged a finger. ‘But are they really going to take the most obvious route? I doubt it. They’re going to be looking to evade the police roadblocks and they’re certainly not going to risk attracting attention by breaking the speed limit. So,’ he clicked off the penlight, ‘that should buy us a little more time while the police get the cordons in place around the mainline stations.’

He paused as someone came into the room wheeling a trolley bearing two silver pots of coffee and tea and a plate of Digestive biscuits wrapped in cellophane. The banal, everyday business of refuelling the human body during a massive live counter-terrorism operation.

‘In the meantime,’ the senior investigating officer continued, once the door was closed, ‘this team needs to be zeroing in on the individuals in possession of the canisters. Now, we’ve had a bit of a breakthrough on the ringleader, this woman Niamh. Well done to Jonathan and his team.’ He nodded at a fair-haired man in a green jersey. ‘Her true ID is Charlotte James, aka Lotti James. She’s a biochemist from Cambridge. Trained in Germany. VX reports her cropping up on the periphery of a German intelligence-service investigation into far-right extremist groups in Saxony. She’s a one hundred per cent fanatic, totally committed to their cause.’

Listening to this, Angela had a sickening feeling she had forgotten something so important it should have been mentioned right up front. The stress and exhaustion of the last few days must have been catching up with her. How else could she have neglected to tell them this? She raised her hand.

‘Our guy Luke Carlton has a lead on one of the Bravos in the warehouse. He told me he’s met him before.’

‘Sorry, what?’ The SIO sounded incredulous. All eyes turned to look at Angela and she could feel herself blushing under their gaze. ‘I should have been told this, Angela.’