'And you have no idea where she went after that?'

'Course not. I came back here. Had some work to finish off.'

'Can anyone confirm that?'

'Give me a break. I live on my own.' He spread his hands wide as if it should be obvious.

'Why didn't you come forward with this information?'

Bourne shrugged. 'Why should I? I've got nothing to say.'

'As I said, it's very important we trace her movements leading up to when she was killed. It's been in all the papers and on TV. Surely you were aware of that?'

'I just had a drink with her, for Christ's sake. It's not a crime, is it?'

Bourne was being overly defensive and Tartaglia sensed he was hiding something.

'You say you were friends, Mr Bourne.'

'That's right.'

'More than friends, perhaps?'

Bourne gave Tartaglia a quizzical look. 'What, me and Rachel? You must be bloody joking.'

'Why's that so incredible?'

Bourne shook his head despairingly. 'Rachel's not my type. Wasn't, I should say.'

'What do you mean?' Feeney cut in.

Bourne sighed as though it were obvious. 'No chemistry, you know. Just one of those things. You either have it with a woman, or you haven't. I'm particularly fussy, as it happens.'

'Did you have dinner with Miss Tenison afterwards?' Tartaglia asked, thinking back to the scraggy little blonde he had just seen leaving Bourne's flat. Rachel Tenison had been a lot better looking, although looks weren't everything.

'No. It was just a drink.'

'You didn't stay the night?'

Bourne rolled his eyes as though he had never heard anything so ridiculous. 'Jesus. Why can't you guys listen? I told you. It was just a drink, so stop trying to jerk my chain.'

He was sweating and Tartaglia wondered if it was just the heat of the room, the dope, or simple nerves. Whatever it was, he was sure Bourne was lying.

'Could you tell us where you were Friday morning?'

Bourne looked blank. 'Friday?'

'Yes. Between seven and nine.'

'Here. Told you, I came back here after seeing Rachel. You trying to catch me out, or something?'

'Just checking Mr Bourne. Are you sure nobody can confirm that you were actually here?'

Bourne gave him a glassy-eyed stare but said nothing.

'As you had a drink with Rachel Tenison at her flat, it would be helpful if we could take your fingerprints. That way we can eliminate them from the others we've found.'

Bourne's mouth hardened as if he didn't like the idea. 'I'll think about it.'

'It really shouldn't take much of your time, Mr Bourne. DC Feeney here can arrange it. I understand there's a fingerprint machine at Notting Hill station. We can also take a DNA swab at the same time.'

Bourne jerked his head forwards. 'What, am I a fucking suspect?'

'We just want to eliminate you from our enquiries.'

'Yeah, yeah, that old cliche. I can see where this is going. Can't you be more inventive?'

'You obviously want Miss Tenison's murderer to be found?'

'What do you think?' He glared at Tartaglia for a moment before tossing back his head. 'Look, of course I want Rachel's murderer found. But I didn't kill her and I have no intention of giving you a swab and having my DNA find its way onto the national database. I know my rights. You lot think DNA's the magic bullet, don't you?' He pointed an accusatory finger at Tartaglia.

'No...'

'Well, I can give you chapter and verse on what's wrong with it. I've done a piece on it for one of the Sunday supplements...went into all the cock-ups...how the statistics are misleading, how easy it is for third party transfer, how basically it's not what it's cracked up to be.' He checked the points off vaguely on his fingers as he spoke. 'So, if you want my DNA, you'll have to arrest me first. And you've got no grounds for that, have you? Now stop wasting my time and leave me in peace.'

Pulling his dressing gown around him, he got unsteadily to his feet and started towards the front door. Having no other choice, Tartaglia and Feeney followed suit.

'No, you're right, Mr Bourne,' Tartaglia said. 'At the moment, we haven't got enough to arrest you. Thank you for your time. If you think of anything else, please give us a call.' He put his card on the kitchen counter.

'Sure, but don't hold your breath.' As Bourne held open the door for them he looked Tartaglia blearily in the eye and flashed a wide, toothpaste smile. 'By the way, I've got a good one for you. How does a nutter find his way out of the woods?'

Tartaglia frowned. 'Is this a joke, Mr Bourne?'

'Yeah. Just up your street. He follows the psycho path.' He was still grinning at his own humour as he slammed the door behind them.

'Jesus wept,' Feeney said, stony-faced, as she followed Tartaglia down the corridor. 'What an arrogant prick. He thinks he's God's gift, doesn't he?'

'He certainly does,' Tartaglia replied, starting down the stairs. 'Unfortunately he's also right. We're nowhere near having enough to arrest him and that's the only way we'll get his prints and DNA off him. In the meantime, I want a thorough background check on Jonathan Bourne. I'm sure he's hiding something and I want to know what it is.'

As they walked out of the building into the drizzling rain and started down Portobello Road, Tartaglia's mobile began to ring. He stopped to shelter in a doorway and, flipping it open, found DS Sharon Fuller at the other end.

'I've just had Patrick Tenison on the phone,' she said. 'He wants you to call him. He was quite insistent. He wants to know if there's any progress.'

'OK,' he said reluctantly, imagining how Tenison would think it his due. Appeasement without information was what was required. Tenison might be next of kin, but he had no alibi for the time of his sister's murder, although so far there was no clear motive to mark him as a possible suspect. 'On second thoughts, ask Carolyn Steele to call him back. She's very good at the old soft-soap. Is there anything else?'

'Yes. I've just taken a message from a Dr Huw Williams. That's apparently spelt the Welsh way. He was very particular about it on the phone. Anyway, he says he was Rachel Tenison's psycho something or other. His rooms are in Harley Street and he can see you at four p.m. He said he has some information we might find useful.'

12.

'Please take a seat. Dr Williams will be with you in a minute.'

The short, grey-haired receptionist closed the door behind her, leaving Tartaglia alone in the waiting-room.

He took off his wet jacket and hung it on the coat stand in the corner next to the window. The sky was already dark and there was little to see other than the outline of a tall crane and the backs of the buildings beyond, all of which appeared to be offices. The room was expensively, if unimaginatively, furnished, with a collection of comfortable-looking sofas and chairs and old-fashioned prints of London views on the walls. The smell of fresh coffee drew his attention to a tray on a table under the window, laid with thermos jug, cups and saucers, milk and sugar. He unscrewed the lid of the jug and poured himself a full cup. He had only had a sandwich for lunch and he was already starting to feel hungry, his energy beginning to flag. He added a little milk, then turned, cup in hand, to examine the rows of glossy magazines laid out neatly on the centre table. He was about to sit down with a copy of GQ when the door swung open and a heavily built man with thick, curly brown hair, strode into the room.

'Inspector? I'm Huw Williams.' He held out a powerful hand. Wearing a well-cut dark suit and pale yellow shirt without a tie, he looked to be in his late forties and not at all like the grey-bearded, bespectacled stereotype of a shrink Tartaglia had been expecting.

'Let's go into my room so we won't be disturbed,' Williams said with a businesslike smile. 'Bring your coffee with you if you like.'

Williams's office was at the front of the building. The blinds were drawn and the lighting low, giving the room a cosy feel in spite of the lofty ceiling. A large, old-fashioned desk occupied one corner and at the other end of the room, a pair of low-slung chrome and black leather chairs faced one other, next to a daybed. A small, round white formica table was placed in the space between the two chairs and highlighted from above by a spotlight. It was all carefully staged and reminded Tartaglia of a TV chat show set.

Williams gestured Tartaglia towards one of the chairs and sat down in the other, his back to the shuttered windows.

'It's good of you to contact us, Dr Williams,' Tartaglia said, taking his seat.

'I would have called sooner but I've just got back from a trip. I had a shock when I saw the papers this morning.' Williams's face was shadowed and Tartaglia found it difficult to read his expression, although his deep, resonant voice was somehow accentuated by the lack of light.

'I understand that Rachel Tenison was your patient.'

'That's correct, until August last year. My background's in medicine and psychiatry but I now practise as an analyst. I saw Rachel pretty regularly for about nine months and I was very sad to learn of her death, particularly given the circumstances.' Williams paused and cleared his throat as if he didn't know what to say next.

'I understand you have some information which may be useful to the investigation.'

Williams placed his elbows on the arms of his chair and steepled his fingers under his chin. 'Criminal psychology isn't my field but I imagine it's just as useful to profile the victim as it is the killer.'

'Yes,' Tartaglia said, taking a mouthful of coffee and putting the cup and saucer down on the table. 'The problem is, I'm finding it difficult fleshing out a picture of Miss Tenison. I feel there's a lot missing. Can you start by telling me why she came to see you?'

Williams took a deep breath. 'Like most of my patients, Rachel was experiencing problems in her life. As you probably know, she lost her immediate family in an accident when she was very young. Rightly or wrongly, she saw this as the root cause of her general unhappiness.'

'How often did she come to see you?'

'Usually once a week.'

'That's roughly thirty-six hours,' Tartaglia said, doing a quick mental calculation. 'You must know a great deal about her.' For a second, his mind turned to Liz, wondering if she even knew of Williams's existence. 'I'm particularly interested in her personal relationships, men in her life, you know the sort of thing. There's a good chance the killer was someone she knew. There's also potentially a sexual motivation to the crime.'

Williams nodded slowly. 'I understand, but it's not that simple. Patients come to see me with a wide range of problems; they're having difficulties at work, say, or in their marriage. Over time, the real underlying issues emerge, but not always. With Rachel, I barely glimpsed beneath the surface.'

'Surely something came out about her private life,' Tartaglia said impatiently, hoping this wasn't going to be a waste of time.

'Of course. She talked about her stepbrother, Patrick, and his family. They seemed very close. Issues with her business partner, Richard, came up on a pretty regular basis but they were quite petty and probably not of interest to you.'

'Did she mention the fact that she and Richard Greville had had a long-standing affair?'

Williams smiled. 'No. There was no mention of it, which doesn't surprise me. Rachel was not someone who liked to talk about emotional issues.'

'But the affair finished at least a year ago, according to people we've spoken to. Why would she mind talking about it?'

'Even if the affair was over, she wouldn't want to risk delving into it. She was quite closed, self-contained if you like, and very controlled. She was also highly intelligent and I realised early on that our sessions were conducted on her terms, not mine.'

'But she must have thought you could help her in some way.'

Williams made a movement with his hands to signal agreement.

'Do you deal with sexual problems?'

'Quite often. I'm not a sexual therapist but naturally I come across sexual problems in my work. Usually, they are symptoms of other underlying problems.'

'From what we know, Miss Tenison was into S&M. She liked being tied up. I can't go into the details of her murder, which haven't been released to the public, but there were elements of it in the way the killer presented her body. We're trying to figure out how it all links in. Is there anything you can tell me which might help?'

Williams nodded slowly. 'With regard to Rachel specifically, I had started to guess that there was something she wanted to keep hidden from me. In one of our sessions I caught a glimpse of it. She described a dream she had had and it became clear she had a fantasy about being raped.'

'Raped?'

'You sound surprised, but it's actually quite a common female fantasy. It's all about dominance and submission, not rape in the real sense of the word.'

Tartaglia thought of the photograph of Rachel Tenison he had taken from Steele's office and the look in her eyes, paradoxically innocent yet mischievous. 'How does somebody get into this sort of thing?'

'Usually someone else will initiate it, suggest they try something new, someone who may be older or more experienced or in a position of power in the relationship. They then discover that they like it and it develops from there. Often they end up taking things a stage further or in a different direction.'

With a sudden flash of intuition, Tartaglia wondered if Richard Greville had been the initiator. It explained a lot of things about the dynamics of their curious relationship and why Rachel Tenison had finally thrown him over. She had moved on. 'Going back to what you were saying about her having a rape fantasy,' he said. 'Why pretend it was just a dream? Why hide what was really going on from you?'

Williams smiled. 'Oh, it's quite common in people with sexual perversions.'

'Really?'

'I'll give you an example. A colleague of mine had a patient who came to see him twice a week for nearly two years. You'd imagine he'd know the man pretty well, wouldn't you? Well, it wasn't until the man was found dead at the bottom of a friend's swimming pool, having drowned himself apparently by mistake, that my colleague discovered that the man practised autoerotic asphyxiation.'

'I thought they usually tried to hang themselves or put bags over their heads.'

'Drowning has the same effect. It's all about cutting off the air supply. Anyway, the long and the short of it was, the poor man had been happily tying weights to his feet and half-drowning himself for years, until one day it all went wrong and he dropped the scissors, or whatever he normally used to cut himself free. My point is, in all that time, he never once mentioned his habit to his analyst.'

'That's extraordinary.'

Williams shrugged. 'People with sexual perversions tend to be devious. You have to see them as just another type of addict, hooked on their own particular drug. Why would they want to mention it to someone like me, who might suggest they stop?'

'Then why come and see you in the first place?'

'Because they're depressed or unhappy about something else. They don't see their habit as the problem; they think they can control it. It's all carefully compartmentalised and a lot of them manage to lead perfectly normal lives on the surface.'

'How the hell can their family and friends not have any inkling?' Tartaglia said, thinking of Liz.