Kate played out the point and suggested they call it a day. They shook hands and walked towards the changing rooms, in time to catch sight of their quarry speeding out of the car park behind the wheel of a blue Audi A5.

‘Shit,’ Kate muttered, under her breath.

‘You want to hold off until tomorrow?’ Julie said.

‘No.’

Kate wheeled right out of Reception, said a curt farewell to Tess Winkelman, who seemed briefly to entertain the idea of joining them, then ripped the keys from Callum’s hand and installed herself behind the wheel of their Peugeot.

‘You think she knew who we were?’ Julie asked.

‘Yes.’

‘How come?’ Callum asked.

They both ignored him.

‘Turning left ahead,’ Julie said.

Kate accelerated hard until they were close enough to sit comfortably on the Russian’s tail. They swung down on to a road that curved around the edge of the Bosphorus and hurtled towards the 15 July Martyrs Bridge.

‘She’s going somewhere she can dry-clean,’ Julie said.

‘What’s that?’ Callum asked, from the back.

‘To check she’s not being followed – or, in this case, to work out who we are, who we work for and how many there are of us.’

‘How does she do that?’

‘Goes somewhere she can move from quiet places to crowded streets and back again. In the former, she works out how many of us there are. In the latter, once she knows how many pursuers she has, she can take a look at us and lose us if she decides she wants to.’ Julie turned to Kate. ‘She’ll use the bazaar or İstiklal Avenue and Taksim Square – or maybe both.’

Kate thought of the last meeting with Lena in the Grand Bazaar before she had forced her aboard Igor Borodin’s super-yacht. It had been Kate’s call to recruit Lena, to bully and blackmail her into working for SIS and push her head first into the lion’s den.

‘I know what you’re thinking,’ Julie said. ‘It wasn’t your fault.’

Kate glanced at her friend. She was assailed suddenly by the visceral image of Lena’s naked body stuffed in a wardrobe on the Greek island of Andros. Hadn’t she, on some level, always known how it would end? ‘I appreciate the sentiment,’ she said, ‘but we both know it was.’

‘What’s happening with Maja?’ Julie asked.

Kate thought of the locket Lena had asked her to give her young sister in Belgrade once they’d made good on their promise to bring her into the UK. It was still burning a hole in her pocket.

‘Still waiting,’ Kate said.

‘I bumped into your aunt outside Ian’s office the other day. I asked her about it. She said, “Soon.”’

‘I’m keeping up the pressure,’ Kate said. She didn’t want to get into Ian’s attempts to block the whole thing.

Julie had been right about Natasha Demidova’s target. The Russian pulled into a car park close to the bazaar and emerged a few moments later on to Yeniceriler Street.