She managed a weak smile. 'I think you're probably right.' She led us out to the front door and stopped in front of it. 'Thank you both for coming. It's very much appreciated, I promise you. Even if it's not that obvious. And I do apologize for getting so emotional. It's very difficult…'

We both told her once again that we understood entirely. With that, the door opened and we were out of there.

There was a pub a few miles down the road and we stopped for a drink and an early lunch. It was empty and we ordered our drinks from the bored-looking landlord and took a table in the corner.

'What did you think of it in there?' Malik asked, sipping his orange juice.

I knew what he was getting at. 'I detected a bit of an atmosphere and I got the feeling that maybe Mr Fox felt a little guilty about something.'

'Yeah, that crossed my mind. Do you think, you know, anything ever went on between him and Miriam?'

'It happens. It happens in a lot of families, rich and poor. And I suppose it would explain a lot: like why she went away in the first place, why she put up with a life as an underage prostitute, why she never made contact with them. But we might be completely wrong. I get the impression she was a difficult kid anyway. Anne Taylor called her a real bitch when she was talking about her, and not even to phone your mum or your sister through all that time…'

'It makes me think that maybe now we've got a motive for Wells. If she had that sort of difficult personality, and it looks like she did, then she could easily have had a major falling-out with him.'

'It's possible.'

'Maybe he thought he was being clever by making it look like a sex crime.'

'It's certainly a viable theory.'

'But you're still not convinced?'

I sighed. 'Not entirely, no.'

'There's a lot of evidence building up, Sarge.'

'Yeah, there is, but there are unanswered questions too. Stuff that puzzles me. Like why Wells came back to the flat.'

'Maybe he's just thick. Plenty of criminals are.'

I told him about the phone records. 'It looks like she and Carla had at least five conversations in the last weeks of Miriam's life. What I can't understand for the life of me is why Carla would pretend not to know her, when it's clear she did. Not unless she had something to hide.'

'And you think it might have something to do with the murder?'

I shrugged. 'I don't know. All I know is that I don't like unanswered questions, and I don't think there's an innocent explanation for it.'

'I told you there was something dodgy about her. I could see it right from the first minute. So, what do you intend to do about it? There's no way Knox is going to want any extension of the inquiry. Not now he's got Wells.'

'I'm going to go and see her, Asif. Make some excuse why we need to talk, then spring it on her.'

'Are you sure that's the reason why you want to see her?'

I gave him a withering look. 'It's definitely the most important reason.'

'Well, let me know what you find out. Although I still think it was Wells who did it.'

Our food arrived. A tired-looking ham salad for me, a chilli con carne that bore more than a passing resemblance to dog food for Malik. The landlord gruffly ordered us to enjoy our meals, although I didn't think there was much danger of that.

'Don't say anything about this thing with Carla Graham to anyone else,' I told him, taking a bite of stale bread. 'Capper got wind that I was getting the phone records off Hunsdon and he told me to leave it alone. I don't want to give him any more ammo to fire at me. Not now he's the boss.'

'Don't worry, I won't say anything.' He spooned down a few dollops of chilli, then looked at me seriously. 'You know, I thought it was bad them making him acting DI instead of you. You could do that job one hell of a lot better.'

'It's all politics, Asif. If you play the game, you go places.'

'Then why don't you play the game, Sarge? Forgive me if I'm speaking out of turn, but you're wasted at DS level. You should be running murder investigations, not just being a little cog in them.'

I forced down a fatty lump of ham, then pushed the plate away. I wouldn't have enjoyed that meal if I hadn't eaten for a week. 'I play it,' I said, lighting a cigarette, 'I just don't play it with the same enthusiasm any more, now that the rules are always changing.'

'You can't live in the past, Sarge. The world changes. Even the Met changes. The secret's to adapt. Change with it. Learn the rules. You could still go places.'

'They made you DS, didn't they? Put you in Capper's role.'

He looked surprised. 'How did you know? Knox only phoned me last night. He said he wasn't going to announce it until this afternoon.'

'He hasn't said a word. Not to me, anyway. I guessed. There was something on your mind this morning when we drove down here. You were quieter than usual. Also, you were the obvious choice.'

'You think so?'

'Yeah, I do. You're a fuck sight more talented than any of the other DCs we've got. You'll make a good DS. When's it effective from?'

'Monday, if it all gets sorted out.' I took a drag on my cigarette but didn't say anything. 'You're not pissed off are you, Sarge?'

I turned to him and smiled. 'No. I'm glad it's you and not anyone else. Congratulations. You deserve it. Unlike Capper.'

'You know, I don't want to sound clichéd or anything, but I've learned a lot working with you. It's been a real education.'

'Don't overdo it. It's me you're talking to, not the DCI.' But I was secretly pleased. I'm just like anyone else. I like compliments, even if they're not entirely truthful.

'Well, I mean it, anyway.'

He went back to eating and I went back to smoking, blowing my cancerous fumes up at the olde worlde beamed ceiling.

'Thanks,' I said. 'It's appreciated.'

Ten minutes later we were back in the car, heading home.

We weren't back in Islington until close to five o'clock. An accident on the M40 had caused massive tailbacks, and since neither of us had any idea of alternative routes, we were forced to crawl along at ludicrously slow speeds for hours with thousands of other irate drivers.

I got Malik to drop me off near home. Somehow I couldn't face going back to the station where the talk would doubtless be of promotions and terminal illnesses, and where I suddenly felt as much an outsider as I ever had. Welland had been an ally, a man who'd often stood up for me in the past. Now he was gone. As a replacement, Capper had to be what a media commentator would call 'the nightmare scenario'.

When I got in I checked my messages. There were none on my home phone, but Raymond had left one on his mobile. He wanted to see me as soon as possible and gave me a number to call back on. He signed off by saying it was urgent, but nothing to worry about too much, whatever that was meant to mean. It was unlike Raymond to leave messages for me, unless it was important. I phoned the number he'd left but it too was on answerphone service, so I left a message for him saying I'd meet him at our usual spot at two the following afternoon unless I heard otherwise. I wanted to see him anyway. There was, it was fair to say, a lot to discuss.

After that, I tried Carla Graham, but she'd left Coleman House for the day and I didn't want to risk calling her on her mobile. She might wonder where I'd got the number from. I told the woman on the other end of the phone that it was the police and asked when Carla was expected back. I was told she was on weekend day shifts and would be in the following morning. I said I'd call her then.

Outside it was raining, but I fancied a walk, and maybe a drink somewhere, so I strolled round the corner to the Hind's Head, a quiet little place I frequented occasionally.