Behavioural detection officers were plain-clothes officers skilled at spotting unusual behaviour in crowds. They looked out for groups who were deliberately keeping themselves apart, for people paying too much attention to their surroundings and for those whose body language suggested a criminal intent.

‘One more thing, sir,’ said the Gold Commander as Tennant sat down at an empty terminal and began to log in. ‘It seems the NRF have been busy.’

Tennant looked up. ‘In what way, Tom?’

‘Officers have picked up leaflets on the ground, claiming to have been published by the National Resistance Force. It’s the first time they’ve been leafleting at Wembley to our knowledge. We’ve got eyes on the crowd and not seen anyone distributing them. It’s the usual stuff – war against Muslims, blah, blah, blah. What’s a bit more out of the blue is they’re claiming Islamists are planning an attack on London within days. Lucky guess, I suppose.’

A bloody lucky guess, thought Tennant as he settled back down at the computer.

His mobile rang. ‘Excuse me,’ he said, rising to walk to one of the smaller offices.

‘This is the Downing Street switchboard, I have the Home Secretary for you,’ announced a prickly voice.

There was a pause and a click before Hogarth came on the line. ‘Assistant Commissioner. Why the hell are you allowing Wembley to go ahead?’

‘With all due respect, ma’am, cancelling the match would be the worst thing to do right now,’ said Tennant, failing to hide his exasperation. ‘Cancel Wembley and we’ve got ninety thousand people on the streets, buses and Tube, all heading to the perimeter of a closed-off stadium and exposed to any terrorist. Keep them in the stadium and they’re behind a security wall – everyone entering the stadium is searched for weapons.’

‘What about the marathon? And this gay march?’

‘The same argument applies, ma’am. We have marchers assembling – and we have marathon runners assembling.’

‘It’s your call, Assistant Commissioner. I have no desire to interfere with operational matters. But I want regular updates. And is DSU Gabriel still handling the investigation?’ There was no attempt to disguise Hogarth’s contempt.

‘Yes, Home Secretary,’ said Tennant. ‘As I’ve said many times before, she has my complete confidence.’

‘I see.’ Her voice made it clear that she didn’t. ‘Feel free to speak to Nina O’Brien – my spad – if I am unavailable. I expect to be kept informed and I expect the public to be protected. No more cock-ups.’ She hung up.

#

Stonebridge, North West London

DC Kathryn Jenson had been door-knocking for twenty minutes. Bose had taken the one-mile-radius circle surrounding the Black Box Storage Company and split it into eight and Jenson had been allocated to the northwesternmost sector closest to Wembley. It was traditional, tedious legwork – knocking on the doors of shops, pubs and community centres, starting at the circumference and working inwards.

Jenson was using an iPad to mark her route along the row of dirty grey 1920s semis that sat within coughing distance of the dual carriageway, plastic window frames blackened with a layer of exhaust and dust. The Islamic Cultural Centre was her next stop. It had been created in a converted car showroom set back from the road behind a row of bollards. The sign above the door was painted in yellow – it looked more like a carpet warehouse, thought Jenson. The mosque was in a conversion to the rear; at the front was a cafe.