‘What effect do you think it’s going to have in court, John, when Alison takes the stand and tells the jury how you asked her to lie for you? You played the devastated bereaved brother in front of her, and then asked her out to dinner, and the poor bitch was so delighted to have a chance to look like a desirable female in front of Tony that she agreed. A couple of dates later, you persuaded her to say she saw you at the office on the morning before Lula died. She thought you were just overanxious and paranoid, didn’t she? She believed that you already had a cast-iron alibi from her adored Tony, later in the day. She didn’t think it mattered if she told a little white lie to calm you down.

‘But Alison wasn’t there that day, John, to give you any files. Cyprian sent her off to Oxford the moment she got to work, to look for Tony. You became a bit nervous, after Rochelle’s funeral, when you realised I knew all about that, didn’t you?’

‘Alison isn’t very bright,’ said Bristow slowly, his hands washing themselves in dumb show, and his knee jiggling up and down. ‘She must have confused the days. She clearly misunderstood me. I never asked her to say she saw me at the office. It’s her word against mine. Maybe she’s trying to revenge herself on me, because we’ve split up.’

Strike laughed.

‘Oh, you’re definitely dumped, John. After my assistant rang you this morning to lure you to Rye—’

‘Your assistant?’

‘Yeah, of course; I didn’t want you around while I searched your mother’s flat, did I? Alison helped us out with the name of the client. I rang her, you see, and told her everything, including the fact that I’ve got proof that Tony’s sleeping with Ursula May, and that you’re about to be arrested for murder. That seemed to convince her that she ought to look for a new boyfriend and a new job. I hope she’s gone to her mother’s place in Sussex – that’s what I told her to do. You’ve been keeping Alison close because you thought she was your fail-safe alibi, and because she’s a conduit to knowing what Tony, whom you fear, is thinking. But lately, I’ve been getting worried that she might outlive her usefulness to you, and fall off something high.’

Bristow tried for another scathing laugh, but the sound was artificial and hollow.

‘So it turns out that nobody saw you nip into your office for files that morning,’ continued Strike. ‘You were still hiding out in the middle flat at number eighteen, Kentigern Gardens.’

‘I wasn’t there. I was in Chelsea, at my mother’s,’ said Bristow.