Abbot nodded. ‘There’s nothing there, though, Chris. Half a shadow across a windscreen, but I couldn’t even tell you if it was a man or a woman.’

‘Okay,’ Foster said. ‘And there’s been nothing else?’

Keller shook her head slowly. Foster guessed her life was pretty routine: a series of arrivals lounges, hotel rooms, training days, match days and then departure lounges, before the whole process started again in a brand-new city. Same meals. Same staff. Same old, same old. If there had been anything unusual, he believed she would remember.

‘Did all of this come through the post?’

Keller shook her head.

‘It appeared in my kit bag. Like magic.’

‘Like magic?’

‘During my first-round match at the French Open. I’m pretty sure it wasn’t in my bag when I went out to play, but it was there when I got home. That’s what scares the shit out of me. Whoever did this must have been able to get access to restricted areas.’

Foster nodded. ‘I can’t think of many places that are truly private, in this day and age.’

Keller’s coach snorted. ‘We’ve been here thirty minutes,’ she said suddenly. ‘You don’t take a single note. You write down nothing. Not very professional, I think.’

Foster kept his eyes on Kirsten. ‘I don’t need to write things down. I notice things, and remember them. It’s my job.’

Rosario snorted again.

‘You bit your nail when the rest of us were looking at Kirsten’s letter,’ Foster said. ‘You snapped the acrylic right off, by mistake. You thought nobody noticed and you slipped it into the left pocket of your tracksuit. It’s there right now.’

On instinct, Tom Abbot and Kirsten Keller glanced at Rosario’s fingers. A flicker of embarrassment played across her eyes for half a second, but then she shrugged and said nothing.

‘You also thought I didn’t notice you texting a taxi firm under the table three minutes ago, because you think this meeting is almost over. But before you go, let me give you some advice. If you ever meet a close-protection officer who needs to write things down, for God’s sake don’t hire him.’

Abbot suppressed a smile.

‘It’s a good trick,’ Rosario said coldly.

Foster’s face was impassive.

‘Which bit?’

Rosario shrugged, gathering up her things.

‘The eyes under the table.’

‘I learned it at sniper school,’ Foster said. ‘Back in the day.’

‘What else did you notice while you were spying on me?’

Foster smiled. ‘Surely you don’t want me to say in front of everybody else?’

He held Rosario’s angry gaze. After a few uncomfortable seconds she swore and then pushed up from the table. Keller stood up, too, and put a restraining hand on her coach’s arm.

‘This is not helpful,’ she said. ‘Why don’t you wait downstairs?’