The estate agent bent down slowly to pick up her clipboard without taking her eyes off me.

‘Is this leasehold?’ I asked, trying to suppress my reawakened pot-based euphoria.

She shook her head.

‘Oh, so it’s freehold,’ I said, ‘a bit like this.’

I lifted my hands and wiggled. She screwed up her face in utter disgust, then bolted.

I popped into a corner shop for a diabetic fizz fix but failed to get as far as the fridge.

Blaring out from today’s Sunday News: ‘Judas Kiss’ by Fintan Lynch, over a photo of Karen Foster kissing Peter Ryan fully on the lips. Peter’s wearing a morning suit because the grainy image is a still from his wedding video.

Tender embrace … the lovers share a kiss just a few feet from Marion, Peter’s new wife. Now Peter’s mistress Karen is prime suspect in the hunt for Marion’s killer …

My hands shook as I read a couple of the more damning revelations from Karen Foster’s police interview. I couldn’t believe it: Shep had leaked her statement and the wedding video to Fintan. A scene replayed in my mind from Thursday night: Shep signing for two packages, one from Woolwich CID, the other from a data transfer company. He must have got a copy of Marion and Peter’s wedding video made to give to Fintan.

Clever Shep. How could the CPS lawyer not charge Karen Foster, now that the world knew the truth?

Another realisation abruptly stopped me applauding Shep’s ingenuity. The team – and the Met Commissioner – would want to know how Fintan Lynch of the Sunday News got his hands on not one, but two pieces of evidence critical to an ongoing murder enquiry. Well, Commissioner, guess who works on the team? Step forward Donal Lynch, younger brother of the journalist who broke the story.

My mind was spinning. Shep knew everyone would suspect me of supplying this material to Fintan. He leaked it anyway. Fintan knew everyone would assume that I was his snout. He ran it anyway. Judas Kiss indeed.

By the time I got to Fintan’s street in North London, I’d convinced myself that he and Shep had plotted this from the very start. My very invitation to join the investigating team had been a ploy cooked up in their Machiavellian imaginations. Both were chess players: they knew they’d find a way to prosper while letting me take the fall. What they couldn’t have anticipated was that I knew the identity of the real leaker.

I couldn’t wait to deliver this little checkmate.

I rang Fintan’s doorbell over and over. Finally he appeared, dishevelled in shorts and my Sonic Youth ‘Goo’ t-shirt. Fucker.

‘What do you want?’ he squawked.

‘You’ve really fucking done it this time,’ I muttered through gritted teeth, barging past him into his barely-furnished bachelor pad.

‘Hey,’ Fintan called after me as I stormed into the tiny nightclub that passed for his kitchen.

‘Who’s that?’

Instantly I recognised her voice, coming from his trendy mezzanine bedroom. Fintan stopped dead in his tracks, opening his arms in a pleading gesture.

‘Look, we were going to tell you,’ he began.

Eve appeared at the top of the metal staircase, wearing my best white linen shirt. I almost expected a serpent and an apple tree. By the time I managed to close my mouth, I’d forgotten why I came here.

‘You’ve been … all along,’ I said, my voice shaking.

‘We never planned it,’ said Eve, quietly.

The sheer scale of their deceit, their betrayal, was too much to take in.

‘Jesus,’ was all I could say.

‘You,’ I said, pointing up at Eve, ‘get the fuck out of my sight, right now.’

‘You,’ I said, pointing at Fintan, ‘outside.’

He led the way, shoulders slumped, head down.

I pinned him against the outside wall, shouted into his wincing face.

‘I’ll have the truth about you and Eve later. Right now, I want the truth about you and Shep, starting at the Feathers.’

Chapter 37

Clapham Police Station, South London

Sunday, August 18, 1991; 11:00

My entrance silenced the incident room. Being last in didn’t help. Trust me to have my first good sleep in years at a murder scene. And Fintan had a lot to tell me.

‘Glad you could join us, Lynch,’ Shep said drily.

‘Sorry Guv, domestic thing.’

I sought somewhere to perch and felt all eyes on me.

He’d turn the team against me now, for sure – if he hadn’t already done so. I’d served my purpose. He was ready to dish me up. I told myself to box clever for once. If I threw my one big shot too early, he could evade it and destroy me. I had to bide my time.

‘I’ve already told the team that the Commissioner has announced a full investigation into how the Sunday News and more specifically, your brother, got hold of Karen’s latest statement and the wedding video,’ he announced.

I hated myself for reddening. I wanted to tell everyone it was anger, not shame.

Shep eyed me coldly.

‘Just to reiterate, we will find out who did this, and that person or those people will never work for the Met police again. As I’m sure you can appreciate, Lynch, this is the last thing we need right now.’

I stood up. Shep squinted, Dirty Harry-style, at the punk not making his day.

‘I am not the source of this story,’ I said clearly. ‘I’ve never passed information to my brother about any case. Think about it. Everyone knows he’s a crime reporter. It would be career suicide.’

Had I got photographs of Shep and Fintan coming out of the Roundhouse pub yesterday, I would have produced them, there and then. As it stood, the only person who could corroborate what I saw was that taxi driver. I scolded myself for not making a note of his driver ID number. All I knew about him was that he was fat, bald, Cockney, objectionable and grasping which, when it came to black cab drivers in London, didn’t exactly narrow it down. I’d pop over to the rank later today, try to trace him. If I was to be the fall guy, I’d do all I could to take Shep down with me.

Shep now adopted a lighter tone: ‘On the plus side, the story has made our lawyer have a re-think. That, and a call from the Commissioner. So our legal eagles are re-examining our evidence against Karen Foster this morning. In the meantime, Laura Foster is in suite three, waiting to be interviewed. Let’s see what we can squeeze out of her.’

As the prime suspect in Leakgate, I didn’t bother asking permission to observe Laura Foster’s interview. Rather than give Shep the pleasure of saying no, I tracked him at distance down that long corridor to the interview suites. As he punched in the secret code to the security door and heaved it open himself, I realised I wouldn’t beat the slam unless I ran. If Shep caught me, he’d send me back – but I’d nothing left to lose.

I launched into a Penelope Pitstop-style series of silent, high-speed, extra-long paces. I felt ridiculous but I caught the door an inch shy of shutting. I expected Shep to turn round at any moment, but he didn’t. Blinkered Olympian speed-walking had proven his downfall again, just as it had when I’d followed him to the Roundhouse pub yesterday.

I followed him into the observation room, took a seat and ignored his lighthouse glare.

The beauty of a two-way mirror is you can stare all you like. Laura Foster was worth a good look. Slim, with lightning blue eyes, she had a pretty, sculpted face and a lithe body – a real beauty. How Karen must have resented her sister’s outrageous good fortune in the genetics lottery.

She wore textbook South London clothing – faded jeans torn at the knees, tight white t-shirt, a chunky gold necklace and a pair of trendy, box-fresh trainers.

The only let down was her voice: like Karen, she spoke in a nasal and whiney monotone.

She sat alongside a podgy man in a tight suit who busied himself with stationery and kept telling her that everything was going to be okay. He looked far more nervous than she did. Just like Karen – and Peter Ryan, for that matter – Laura seemed oblivious to the gravity of the situation. You’d think they got quizzed about a murder every few weeks. I didn’t know whether to put their collective ambivalence down to arrogance, guilt or just plain ignorance.