Tartaglia turned to Clarke. 'You knew Gifford, Trevor. What's your view?'

Clarke shrugged. 'Alan was a hard man to go against. He was a good copper, mind, but he could be blinkered. Once he'd made up his mind about something, that was that.'

'That's sort of what Simon Turner said, reading between the lines,' Tartaglia added. 'I wish he'd been more up front about it.'

'No one wants to speak ill of the dead, do they?' Clarke replied. 'Certainly not a former boss, who was a decent bloke in most respects. I'm sure, in spite of Alan's blinkers, the team did a good a job.'

'As I said, I made my views known to Alan Gifford when Broadbent was arrested,' Harper said flatly, as though she didn't agree. 'I watched all of the interviews with Broadbent on videolink and nothing I saw changed my mind. He didn't match the profile and I stand by that today.'

'If he had been treated more gently, what do you think they might have got out of him?' Tartaglia asked.

'Well,' she replied, with a little nod of her head, 'Broadbent was very fond of Watson, almost to the point of obsession, I'll admit. He followed her around quite a lot when she went out and took photos with a telephoto lens.'

'He did that with other women as well.'

'Yes. It was all pretty harmless, but he was there on the spot over several months keeping an eye on Watson. I just wonder, if Gifford and his team had taken a different line with him, whether Broadbent might have remembered something useful, that's all. Maybe he saw something when he was watching her.'

'If he did, why didn't he say so at the time?'

'Because it might not have meant anything to him and the way they interviewed him was unnecessarily aggressive and confrontational. Again, my advice was ignored. As I said, Broadbent wasn't the sharpest tool in the box and he was already in a highly emotional state because of what had happened. They should have handled him differently, much more sympathetically, if they wanted to get anything out of him.'

Tartaglia made a mental note to speak to Turner as soon as the meeting was over. It was the most interesting thing he had heard in a while and well worth pursuing. Broadbent as witness rather than suspect. They would re-interview him again as a priority, whether Turner liked it or not. 'Thanks. We'll definitely follow it up. You may like to know that Broadbent has an alibi for Rachel Tenison's murder.'

She smiled. 'I'm glad. You should tell him so. If he knows he's in the clear, you might get something out of him.'

'What about the other suspect, Michael Jennings? What was your opinion of him?'

'Oh, from what I saw of him, he was a much better fit. He's the right age group too, whereas Broadbent was too old to be starting this sort of thing up from scratch.'

'Any previous?' Clarke asked, quietly.

'No,' Tartaglia replied. 'Jennings was clean. What did Gifford think of Jennings?'

Harper sighed. 'If you want the truth, he was so set on Broadbent being the killer, I don't think he looked at Jennings as hard as he should have.'

'But they searched his flat thoroughly, twice, according to the report.'

She shrugged. 'All I can say is I was very surprised that they couldn't turn up anything on Michael Jennings. A photograph of Catherine Watson was missing, which I'm sure the killer took as a souvenir.'

'A photograph was also missing from Rachel Tenison's flat. The problem is that neither Broadbent nor Jennings come up anywhere in Rachel's life. We've shown pictures of both of them to all of her nearest and dearest but nobody recognised either of them.'

Tartaglia leaned back in his chair and glanced out of the window at the dark sky. Even though what Harper had said made good sense, there were no easy answers. He still felt miles away from any clear understanding of how the two crimes could be linked.

'Assuming the same person committed both murders,' he said, looking back at Harper, 'don't you think it's odd there's been a gap?'

'A year's not a very long time, particularly if he's new to this sort of thing. As you know, this sort of crime's rarely a one-off, but if he's able to satisfy his urges somehow, either through his memories of the experience or in some other way, that might be enough. He doesn't actually need to kill to get what he wants.'

He turned to Clarke, who was drumming his fingers lightly on the table. 'Any thoughts, Trevor?'

'Maybe the killer's inside, or gone abroad. That's usually where the buggers are when they go off the radar screen.'

'We're trying to trace Jennings at the moment, but we're not having much luck,' Tartaglia replied, deciding that Turner needed one hell of a kick up the arse. 'Going back to the Holland Park murder, Rachel Tenison was laid out in exactly the same position as Catherine Watson.'

'Again, the murderer's making a statement,' Harper said.

'As with the poem in her mouth?'

'Yes. It's about the type of woman she was and it's also about him. He identifies with the obsessed lover, the woman's victim. Maybe he also likes linking her with his memories of Watson.'

'You said the two murders had a few things in common.'

'Superficially, yes. You have the way the bodies were displayed, which we've discussed. Both women knew their killer, a photograph of each woman was taken from where they lived and, on a deeper level, the victim profile is similar. They were roughly the same age, Rachel Tenison was thirty-five and Catherine Watson only three years older, and they were both well-educated, intelligent and successful women in their own fields. They would have been seen as powerful and authoritative and intimidating by this type of man.'

'Is this making any sense to you, Trevor?' Tartaglia asked, looking at Clarke.

Clarke shrugged. 'Maybe you have a copycat killer. Have you thought of that?'

'But why? It's not as if we're looking at a series here.'

'There's another explanation,' Harper said. 'If the same man's responsible for the Watson murder and for the Holland Park murder, it's possible he hadn't intended to kill Rachel Tenison. Maybe it was a sexual encounter that went wrong.'

Clarke shook his head, as though he didn't see it either.

'Going back to Catherine Watson, her killer probably enjoys relatively normal sexual relations with women,' Harper continued. 'They probably have no inkling of his fantasies, no idea what he's capable of.'

'You've got to be joking,' Clarke said, slapping his hand hard on the table. 'How the hell would his wife or girlfriend not know she was sleeping with a sadistic pervert? Surely a woman would know?' He looked meaningfully at Harper.

Harper laughed. 'Trevor, if I had a pound for every time someone reacted like you, I'd be rich. A lot of people keep their real sexual proclivities hidden away. At the extreme end, I can refer you to a number of cases where the partner of a violent rapist or sexual killer had no idea of what actually turned him on.'

Clarke waved Harper away with his hand. 'Yeah, yeah. I'll take your word for it.'

'It's all about fantasy. With some women he can play them out and let himself go, with others he doesn't dare to or doesn't want to. This is a man who keeps his life carefully compartmentalised.'

Tartaglia nodded; her words were a strange echo of what Dr Williams had said about Rachel Tenison: 'On the surface, there's nothing to hint at what is locked away beneath.' It was all tying in, but what it meant, he still couldn't fathom. 'It's weird,' he said. 'You could almost be describing the Holland Park victim.'

'It really isn't uncommon,' Harper added. 'It's just a matter of degree. Like a lot of men with fantasies they'd rather not bring home, the killer may be using prostitutes to keep himself in check.'

'There's nowt queerer than folk, as my nan used to say,' Clarke replied, attempting a north-country accent and still looking unconvinced.

'I thought your family were all from the Elephant and Castle,' Tartaglia said.

'You don't know everything about me, Mark. Still some secrets to find out, you'll be pleased to hear.'

Tartaglia smiled and looked back at Harper. 'What I don't understand is why someone would suddenly do what he did to Watson. Out of the blue, with no apparent build-up to it.'

'We don't know how long the killer had the fantasies playing in his mind, how long he'd been thinking and planning to do something like this, maybe never actually imagining he'd get the chance or go through with it. The trigger could have been something simple, maybe something that Watson herself said or something else going on in his life. Jennings's girlfriend dumped him only a few weeks before Watson's murder. Even though Jennings denied it, friends of his said he was very angry about it. Also, whoever it was may not have intended to kill Watson.'

'Might she have gone along with some of it?' Tartaglia asked, thinking back to Donovan's theory and the possibility of Watson having been in love with someone.

'Yes. Maybe one thing led to another and things got out of control.'

'But you said the killer had everything planned,' Clarke said. 'You said he came prepared.'

'Yes. But being prepared is one thing. Actually doing something is another.'

Clarke nodded slowly and took a sip of water.

'Be prepared. Now you have me imagining the Boy Scouts,' Tartaglia said.

'You're not far wrong, actually,' Harper replied. 'Rather like someone planning an expedition, he may have made a number of dry runs, tested the kit to make sure it worked, packed and unpacked it until he gets it just right. What he wears would also be important to him and he may even carry the kit around with him wherever he goes. Just having it with him, knowing it's there, will excite him and make him feel powerful. He will also dress the part in some way.'

'You're talking about role-playing,' Tartaglia said, thinking of the masks and the other contents of the trunk, the so-called dressing-up box, in Rachel Tenison's bedroom and the way Williams had described her ritual of getting dressed to go out. He wondered what her ritual in the bedroom had been, if she had different roles or fantasies that she played out according to her mood or the man she was with.

'Role-playing, definitely. Going back to the profile, one thing I found interesting and out of character was that he strangled Watson with a pair of her own tights. If he'd come meaning to kill her, he would have brought some sort of ligature with him. It suggests to me that events took him by surprise, perhaps went further than he had intended, and he was forced to improvise. It's why I'm not absolutely certain he intended to kill her.'

'What about Rachel Tenison's murder, then? You said it might have been a sexual encounter that went wrong.'

'She liked being tied up, she liked it rough,' Clarke said, before Harper had a chance to reply. 'They make the perfect couple, don't they?'

'That may very well have been what brought them together in the first place,' Harper said. 'With her, he can indulge his fantasies and he doesn't need to kill her. Although what he does is all about him. I wonder if he'd actually want someone so totally into their own, well-developed fantasy world.'

'But he does kill her,' Tartaglia insisted, still feeling as though they were trying to fit a round plug into a square hole.

'Maybe, for some reason, he was pushed to it. Usually he manages to hold back his more sadistic urges, or at least contain them well enough that nobody reports him. Maybe he meets the Holland Park victim and they go back to her flat for sex. Maybe she does something to anger him or make him feel small. He's a man who likes to be in control, remember, he wants to call the shots. Perhaps she criticises him in some way, or makes him go before he's ready, or something like that. Or maybe he revealed something to her about himself that he didn't want anyone to know.'

'So, the murder was an afterthought,' Tartaglia said, thinking back to the crime scene and all the inconsistencies that still failed to add up. What still puzzled him was the fact that the body had been moved and repositioned after death.

'Maybe.'

'That's a heck of a lot of maybes,' Clarke said, folding his arms and shaking his head again as though he didn't believe a word of it. 'I could paper the wall with them.'

'Why so sceptical?' Tartaglia asked, taking comfort from the fact that Clarke too remained unconvinced.

'These ruddy psychologists. They can spin gold out of the air. And by that I mean fool's gold.'

Harper smiled. 'Now you're in danger of sounding like Alan Gifford.'

Clarke grunted. 'I'm not anything like him and you know it. Seriously, Angela. A lot of what you've said makes sense, but from where I'm sitting they still look like two totally different crimes.'

Harper smiled. 'I don't disagree, Trevor. But Mark asked how the same person could be capable of both crimes. It's the only way I can make it stack up from a psychological point of view.'

'And it's not entirely implausible,' Tartaglia said, feeling suddenly drained by the whole discussion. 'He's killed once before. It would make sense to try and dress the second murder up like the first. He gets the idea of the poem from Catherine Watson's papers. The fact that he decides to use it shows he's arrogant. And speaking of arrogance and attention-seeking behaviour, I wonder if he had anything to do with the press tip-off.'

'Good point,' Clarke said. 'You'd better get onto Jason Mortimer right away.'

Tartaglia felt his phone vibrate in his breast pocket. Seeing Donovan's name on the caller ID, he made his excuses to Harper and Clarke and got up from the table.

'I'm still at Trevor's,' he said, walking over to the window.

'Sorry to disturb,' she said, 'but I've just picked up a call from Liz Volpe. She's trying to reach you. Apparently, she was out running in Holland Park this afternoon and saw something very odd.' He listened as she explained what had happened. The place described sounded like the exact spot where they had found Rachel Tenison's body.

'Have you called forensics?'

'A team are on their way over to the park right now. Karen's going to collect Liz and take her down there so that she can show them where she saw the man.'

'Get Karen to take a statement and see if you can arrange for Liz to do an e-fit afterwards, while it's still fresh in her mind. How did she sound?'

'Pretty shaken. She said she wanted to see you.'

He looked at his watch. 'We're almost done here, then I was planning on heading back to the office. Tell her that I'll be over later at some point. First, I need to talk to Simon Turner.'

22.

By the time Tartaglia got back to the office in Barnes, it was nearly seven in the evening and pitch black outside. The rain had stopped but the wind had picked up and the air felt cold and damp.

He parked his motorbike in a sheltered corner of the car park at the rear and walked over to the back door, the only working entrance to the building. An overweight, middle-aged man and a pretty young woman from one of the other offices stood huddled together in their overcoats just outside, neither speaking, each pulling hard on a cigarette. Sodden butts littered the wet ground where they stood, in spite of a notice and a bin placed beside the exit. It was a horrific vision of what was to come once the smoking ban came into force in the summer. Much as Tartaglia often craved a cigarette, he had managed to wean himself down to no more than five or six a day, usually enjoyed in the peace of his own home or someone else's, with a morning cup of coffee or an evening glass of wine. At least nobody could take away that freedom. But what was the pleasure in standing outside, shivering in the bitter cold, all for the sake of a smoke? You had to be desperate and he wasn't there yet.

With a brief smile of sympathy in the direction of the woman, which she warmly returned, he keyed in the access code and went inside, wishing he had time to stop and talk and wondering which floor she worked on and why he hadn't come across her before. He was halfway up the first flight of stairs when the door on the floor above flew open and Simon Turner burst onto the landing. Whistling loudly and tunelessly, Turner clattered down towards him, backpack and coat in hand.

'Simon, there you are. Can I have a word?'

Turner stopped just above him. 'What is it? I'm running late.'

'Do you know what happened to all the photographs Malcolm Broadbent took of Catherine Watson?'

'No. Why?'

'I was just wondering if Broadbent might have accidentally caught someone else on camera when he was photographing Watson, maybe someone she was with.'

'I doubt it. The shots were mostly close-ups, taken from a distance with a telephoto. A lot of the photos weren't even of Watson, just unknown women walking around in the street. There weren't any of men, if that's what you're thinking.'

'You're sure? You looked through them?'

'I didn't go through them all personally. Alan had a couple of the DCs do that.'

'But Gifford was looking for something to incriminate Broadbent, wasn't he?'

Turner chewed his lip thoughtfully. 'Evidence of the bloke's obsession with Catherine Watson, yes. Broadbent was obsessed,' he said, emphatically. 'There was no question.'

'My point is, Gifford would have told whoever was going through the photos what he was hoping to find. Maybe he didn't tell them to look for anything else.'