Kate stepped into the alley as he turned on his heel, but Julie gripped her forearm. ‘We can’t, Kate. It’s suicide.’

‘It’s all right.’

‘We don’t know who the hell he is! They’re trying to get us somewhere quieter!’

‘We don’t have a choice.’

‘Of course we have a choice!’

The young man was already disappearing into the crowd again. ‘You stay here,’ Kate said.

She turned out of the café and it was a few seconds before she realized that Julie was with her. ‘I’ll follow, you hang back,’ Julie said.

‘No,’ Kate insisted. ‘My show, I take the lead.’

The young man took them on a circuit of the bazaar, too eclectic to be anything but an attempt to work out if there were more than two of them. Julie caught up with Kate as they emerged into an alley thronged with currency traders yelling prices into their phones – a poor man’s Wall Street. They were all men, mostly middle-aged, and the air was thick with smoke and body odour.

At the other end of the alley, the young man picked up the pace. He was no athlete, but fear must have been powering his step, because he hurtled away from the bazaar and up to the Golden Horn Bridge. As they reached Taksim Square beyond it, the business heart of Istanbul, Julie came level with Kate for a moment again. ‘I should call Callum,’ she said. ‘I think they’ll take us up İstiklal Avenue.’

‘Do it.’

Julie fell back. But she was right. For a moment, Kate thought the young man had got on to a tram just by the statue of Atatürk, but he emerged at the other side of it and she followed him all the way down İstiklal Avenue.

He slowed his pace now. He glanced into a café and looked as if he might stop at another serving elaborate Turkish desserts. Was he searching for someone, waiting for a contact?

He came to a halt at a restaurant with a giant slab of doner kebab by its entrance, but didn’t take a seat at the table or look back towards Kate and, for the moment, she made no attempt to approach him. She got out her phone and, as if to check where she was on Google Maps, pulled to the side of the street.

She watched him discreetly out of the corner of her eye as the Turkish lunchtime shoppers flooded past, the secular and the religious, women wearing sunglasses and head-coverings, young men in baseball caps, jeans and T-shirts interspersed with those wearing more traditional forms of Turkish dress. This city wasn’t just where east met west, but where every style of existence appeared to be fighting for its place in the sun.

Now he was approaching her. ‘We’re clear. Get into the car up ahead there.’

‘We’ll follow you.’

‘No. You must—’

‘That wasn’t a suggestion.’

He shrugged nervously. Kate followed him towards a black Mercedes saloon parked just beside a restaurant on the far side of the road. Kate called Callum. ‘Where are you?’