The idea was to move from crowded areas to open ones and back again, while officers on the streets worked behind her to get a sense of what they might or might not be up against. Danny, meanwhile, monitored the electronic activity in the immediate vicinity of her progress to check for any spikes that might suggest hostile officers communicating with each other while in pursuit.

Kate was halfway down Unter den Linden when the tiny microphone in her ear came to life with Danny’s calm, steady voice. ‘Take a turn into Bebelplatz.’

She did so, ambling slowly to the centre of the famous square, in which the Nazis had burnt books, to look through the glass window in the cobbles at its centre, which afforded a view of the library built in memorial beneath.

She returned to Unter den Linden and continued on past Museum Island to Alexanderplatz, which still had the bleak air of the square in east Berlin it had once been.

Despite her leisurely pace, Kate reached the corner of the square early and Danny instructed her to carry on beyond it. ‘Need a bit more to be sure,’ he said.

She walked on under the S-Bahn and swung left into Münzstrasse. Halfway down it, she turned into a vintage shop, where ‘The Eton Rifles’ by The Jam was playing on an old turntable. It was a pick-and-weigh store, where your choices were measured by the kilo, full of ripped jeans, denim shorts, leather belts, bags and jackets, sunglasses and every kind of hat that might have been fashionable in the sixties, seventies or eighties.

As she stepped back on to Münzstrasse, Danny’s voice rang in her ear: ‘Clear. Go back to the meet point.’

Kate retraced her steps, past the homeless people sleeping beneath the underpass, until she was standing by the bus stop in the corner of Alexanderplatz.

She waited. Julie had slipped a packet of cigarettes into the pocket of her jacket before she’d left the hotel and she lit one now to pass the time.

It started to spit with rain, so she joined the bus queue beneath the shelter. An old woman in front of her waved away the smoke.

A phone rang in her pocket. It was not her own. She took out an old-fashioned Nokia and answered it. She had not felt anyone place it there. ‘I said come alone,’ Mikhail said.

‘We’re not at the stage yet where I’m prepared to take that risk.’

‘Go to the S-Bahn station. Head for Westkreuz. Keep the phone with you.’

Kate put the Nokia back into her pocket and crossed the road. ‘He’s asked me to get on an S-Bahn train to Westkreuz,’ she whispered quietly into the microphone hidden inside the lapel of her jacket. ‘How the hell did someone get a phone into my pocket?’

‘Sorry, Kate,’ Danny replied. ‘We didn’t see anything.’