‘Correct. MI5.’ Barron peered up at the ceiling and addressed himself to it. ‘It appears they are engaged in a negotiation with an individual who is asking for certain guarantees.’ He bore back down on Patrick. ‘They gave me a profile of this person and asked for an in-house solicitor who might be able to strike up a relationship with him. I know you’ve only just joined us but you’re the man for the job.’

‘I know nothing about that world,’ said Patrick, bemused.

‘That’s a plus, you can play the innocent. Are you up for it?’

Patrick thought of the dull prospect of his next departmental visit. ‘Yes. Thank you.’

‘I’d been there literally two weeks,’ said Patrick, striding down Nine Elms. ‘Just finished my compulsory two years at the City law firm slave drivers who’d put me through articles. There was a job ad at the Treasury Solicitors. It’s the Government Legal Department now. I applied and got it. They were sending me round the departments. As I remember the next visit was to the Driver and Vehicle Licensing Agency in Wales.’ His grin had been absent for the longest Sara could remember. Now he shot her one. ‘MI5 sounded more exciting.’ The grin didn’t last long. ‘Idiot that I was.’

‘Doesn’t sound like you were being given a choice,’ said Sara.

‘You don’t say no two weeks in, do you?’ He paused as they stopped at the pedestrian lights to cross towards the river. ‘The someone’s name was Walter Thompson. Barron gave me his number and said he was expecting my call. He said hello, gave me a time – 12.45 – and a place. That was it.’

‘Where?’

Patrick pointed airily towards Millbank Tower. ‘Over there. Not exactly St James’s, is it? They don’t do pizza in the clubs there. I arrived five minutes early – wanted to be sure – told a waitress the table was booked in the name of Thompson. She led me to a corner. There he was, reading The Times. Fifties, I guessed, roughly parted sandy hair, mud-brown corduroy jacket with brown leather patches covering the elbows. Oh… and a dark red cravat dangling down over a check shirt.’

‘Patrick Duke.’ The voice was gravelly – an actor’s voice, Patrick thought.

‘Yes, that’s me, Mr Thompson.’

‘J. Call me J. Everyone does.’ Patrick was bemused. ‘Walter Thompson. J Walter Thompson. Geddit?’

‘You mean the ad agency—’