By the time she had completed her first circuit, the park was busy with morning dog-walkers, runners, commuters and children racing around on bikes and scooters, perhaps taking the slow route to school. She had switched on the phone assigned for this morning’s operation and, as she circuited back past the museum, it pinged with a message for the first time. It had no words, merely a picture of a bearded young man dressed in leather jacket and jeans who was roller-blading along a pavement. Kate understood exactly what was meant by it: the Moscow team suspected him of being part of a surveillance unit.

Along the river section, Kate passed Julie for the first time. They did not meet each other’s gaze.

Shortly afterwards, her phone throbbed again. En route.

Kate worked tirelessly, sweeping to and fro across her field of vision, trying to spot anyone whose presence might be unusual or unexplained – anyone who was not settled in the easy routine of their normal morning business. She walked with purpose, as if making more than one circuit was an exercise routine, and she had timed her final lap so that she ought to reach the entry point of Leninsky just a few moments behind Incisor himself, but it was a moment or two before she picked him out.

He wore a fawn jacket and dark slacks and followed a black Norfolk terrier on an extendable lead. Kate’s phone throbbed again. It was a message from Julie: Roller-blades has exited park. Now clear.

There was a reply from one of the Moscow team. Clear.

Kate wiped a bead of sweat from her forehead, though it was not a warm morning. She tried to dry her palms with the inside of her jacket. She held back, let Incisor get ahead, at one point even stopping for a moment to fiddle with her watch, as if checking her rate of progress or pulse rate.

She could see no evidence that Incisor was being followed.

Kate picked up the trail until she reached the Ostrovok Café, where he sat at a table overlooking another boating lake, his dog curled up at his feet.

She took a seat opposite him. ‘I am very sorry to bother you,’ she said, ‘but I am waiting for a man called Boris. That wouldn’t be you, by any chance?’

He smiled at her. ‘No,’ he said. ‘But you’re welcome to join me while you wait.’

Kate did as invited. ‘He is very late,’ she said.

Incisor nodded. He waved at the waitress and a pretty young girl flitted over. ‘A double espresso,’ Kate asked the girl in Russian. Incisor surveyed the menu and then ordered, which gave Kate a moment to study him. He was very thin, with drawn, hungry cheeks and a tattered brown moustache. His fawn jacket was grubby and his cotton shirt and slacks might have been hangovers from the Soviet era.

He waited until the waitress was out of earshot before he turned back to her. ‘Are you from the embassy?’ he asked, in English.