27.

Late Monday morning, Tartaglia was at his desk catching up on paperwork. With Gary Jones still on holiday and Turner out on the road somewhere, he had the cramped, low-ceilinged office to himself and he was appreciating the relative quiet. But try as he might to focus his energies on ploughing through the backlog, his mind kept wandering to the Holland Park case, wishing that somewhere a glimmer of light would creep through.

On the strength of what Liz Volpe had said, plus the two glasses in Rachel Tenison's flat with the same fingerprint, they had hauled Jonathan Bourne out of bed early on Sunday morning and grilled him hard. He had finally admitted that he had gone back to Rachel Tenison's flat the night before she was killed, and had slept with her. It explained the phone call she had made to him around eleven o'clock that night when, according to him, she had asked him to come over. It also explained the two glasses with the same set of prints. But however much pressure they exerted, he stuck to his story: he had left her flat at about five the next morning and had gone straight home. He denied point blank having killed her. He had no alibi, but, as with Patrick Tenison, if Jonathan Bourne had killed Rachel Tenison, there was no explanation for the definite links to Catherine Watson's murder.

Meanwhile, Broadbent had also been re-interviewed, but nothing interesting or new had emerged. Although every effort had been made to treat him with kid gloves and it had been impressed upon him that he was not under suspicion, he had no recollection, two years on, of having seen Catherine Watson in the company of any man. Everywhere they tried seemed to lead to a dead-end; nothing was giving.

Tartaglia looked up at the photograph of Rachel pinned to the board above his desk, and then at the one next to it of Catherine Watson. They seemed so different in every way, one exploited by men right up until the end, the other exploiting mercilessly. What could they possibly have had in common?

Feeling tired from being closeted all morning, he got up and stretched, flexing his shoulders and neck to get rid of the stiffness. His eye fell on the miserable sight of three half-drunk mugs of cold coffee huddled together on his desk, one for each hour he had been sitting there. Deciding to stretch his legs, if nothing else, he gathered up the mugs and walked along the corridor to the office kitchen. The room was small and windowless, having once been a storage room, and even though it was generally kept clean and tidy, it had a permanently stale, unappetising smell. He avoided it whenever he could, but short of going out to one of the many local shops, there was no alternative.

He put his mugs in the dishwasher and almost without thinking switched on the kettle, spooning another helping of instant coffee into a fresh mug from the cupboard. As he waited for the water to boil, he wondered if he should make the effort and go out to get a proper cappucino instead. He had been brought up with good Italian coffee at home and had never managed to acclimatise his taste buds to instant, but he still had a lot of work to finish and it would have to do for the moment.

As the kettle pinged, Dave Wightman put his head around the door.

'Ready when you are, Sir,' he said brightly. 'Shall I set it up in your office?'

Wightman looked unusually fresh for someone who had had little sleep. He had managed to locate and retrieve from store the original disc copies of Broadbent's entire photo collection, made at the time of Gifford's investigation. The files comprised thousands and thousands of jpegs, going back over two years up to and including the time of Watson's murder. Having loaded them all onto a laptop, Wightman had been busy for most of the previous twenty-four hours sorting them into date order.

'Use Gary's desk,' Tartaglia said, filling the mug with hot water. 'I'll catch up with you in a moment.'

Wightman disappeared from view and Tartaglia added an extra measure of coffee to make the brew stronger, followed by a few drops of milk. Satisfied with the colour, he carried the mug back down the corridor to his office, where Wightman was now sitting at Gary Jones's empty desk next to the window, the laptop open in front of him.

Tartaglia pulled up his chair and sat down, peering at the screen, which was filled top to bottom with photographic thumbnails, eight per line, just big enough to make out a basic image but nothing more.

'These were all taken by Broadbent?' Tartaglia asked.

'Yes. There are a few crappy shots taken with a mobile, but he's mostly using two cameras throughout, a serious piece of Nikon kit with a big telephoto and a Canon Ixus 55.'

'What's that?'

'It's a small pocket camera. The zoom's nowhere near as powerful as the Nikon's, but it's a heck of a lot more discreet and portable. I've removed everything after the time of Watson's murder to make it easier and I've re-ordered them into separate folders according to date.'

'I can't tell what's going on,' Tartaglia said, still unable to see anything recognisable.

'I'll make them bigger in a minute. What time frame do you want to look at?'

'Let's start as close as possible to the date of Catherine Watson's murder and work back.'

'OK.' Wightman scrolled to the top of the screen. The folders ran down the left hand side of the screen and as Wightman opened one of them, a series of images sprang up. 'These were taken the day Watson died,' he said. 'The first lot are in Oxford Street. He spent a good few hours there, judging by the times on the pictures. Then there's another batch on a bus, then some more in another street, somewhere a bit more suburban, although I couldn't see a post code or street name anywhere.'

He clicked on the top left picture and enlarged it, showing a view of a crowded pavement, people bundled up in overcoats and scarves, carrying shopping bags, some walking, some gazing at a large, expensive-looking window display. It was a bright, sunny winter's day and the quality of the pictures was good. Tartaglia scanned the faces but nobody looked familiar.

'This lot's outside Selfridge's,' Wightman said, tabbing forwards, showing an apparently endless stream of similar views. 'After that we get John Lewis and Top Shop.'

As Tartaglia looked closer, he realised that the camera was tracking the progress of a pleasant-looking woman with shoulder-length, curly dark hair. She was in the company of another woman who was shorter and plumper with layered, streaky blonde hair. The two walked together along the road, chatting and stopping to look in shop windows. A perfectly normal Saturday, apart from the fact that they were being followed and photographed.

'Is there a lot of this sort of stuff in there?' Tartaglia asked, pointing at the laptop.

'Yeah. It's pretty representative, from what I've seen. He's out with his camera most Saturdays. Seems it's his big day out. He took over three hundred shots in total on this day alone.'

'How many did he take of that particular woman?'

'At least fifty. He only stops when she and her friend go down into Bond Street tube. After that, he follows another woman, and then another. It seems to be quite random, although they all look rather similar.'

'They all look like Catherine Watson, you mean. He's obviously got a physical type he likes. Are all the other photos like this?' he asked, thinking back to what Turner had said about the majority being of unknown women walking around in the street, and wondering if they were wasting their time looking through them.

'More or less, although he's also got a thing about architecture, mainly churches. Some of the shots are quite artistic. He also likes schools.'

'Schools?'

'Never any kids. Just the buildings. And the women.'

'Weird.'

'Takes all sorts, Sir,' Wightman said, as if he'd seen it all in his short life. He tabbed backwards in time.

'Is there any pattern to it? I seem to remember he had some sort of part-time job during the week.'

'Yes. Saturday and Sunday are the busiest, followed by Monday and Thursday. I imagine he works the other three days. The little Canon seems to go with him everywhere.'

Wightman tabbed slowly through the rest of the file, image by image. Almost all of the pictures taken that Saturday were of women, none of them aware of being photographed. As Turner had said, there was nothing illegal in any of it, nothing hinting at a darker, more violent side, but it was still very bizarre and Tartaglia wondered what sort of peculiar mind found satisfaction in doing such a thing.

'Right. That's Saturday over and done with,' Wightman said, once they had looked at every frame. 'The next lot were taken on the Thursday before Catherine Watson died.' He looked down at his notes. 'Yes. Somewhere along the Finchley Road, close to where Broadbent lives, judging by the post code.'

A series of photos followed of a busy road, lined on one side with fruit and vegetable stalls. Cars and buses passed, people thronged the pavement and it was like a thousand other thoroughfares outside the city centre with its halal butchers, fast food outlets and endless cheap clothing shops. Apart from the backs of people's heads, it wasn't clear what Broadbent was photographing. Tartaglia's head was already beginning to swim and he wondered how much more he could endure when he suddenly spotted a familiar face.

'That's her, that's Catherine Watson,' he said, almost rising in his chair. The shot was of a cafe window, with a woman sitting inside. He recognised her even though she was half obscured by the blurred images of people passing in front of the camera. It looked as though Broadbent had been standing on the opposite side of the road with his telephoto. She had a cup of something on the table in front of her and had turned her head to look out of the window at the street. 'Are there any more in the sequence?' he asked impatiently.

Wightman tabbed forwards and they saw her now in profile, her chin resting on her hand as she looked in front of her. He could tell instantly from her body language that there was someone opposite her.

'Can you enlarge it? She's not on her own.'

'Sure. Give me a minute.'

Wightman clicked a few buttons and zoomed in on the table. Tartaglia thought he could just make out the shadowed profile of a face.

'The light's reflecting off the window and I can't see inside clearly. Go forwards and let's see if we can get a better image.'

Wightman tabbed through the shots until finally he found a number taken from a different angle. Maybe Broadbent had been asked to move or couldn't see what was going on inside the cafe.

'Look there.' Tartaglia pointed at the screen. Watson was no longer at the table but there was someone else on the other side. 'Can you enlarge that bit?'

He watched as Wightman enlarged the image, zooming in on a khaki-coloured sleeve and a pair of masculine hands cupped around a mug of something. Wightman tried the next image and then the next until a triangle of face and blond hair were visible as whoever it was bent forwards to sip from the mug.

'I wonder if that's Michael Jennings,' Tartaglia said, remembering the head and shoulders he had seen of Jennings in the file and trying to contain his excitement. 'Can you enlarge it a bit more, see if you can get a better image?'

Wightman fiddled with the keyboard and mouse until the picture gradually became clearer.

'I'm sure that's Jennings,' Tartaglia said. 'Go back to the beginning of the sequence. I want to see all of them now.'

The first twenty frames in the series showed Catherine Watson walking along the road. Now that they knew what they were looking for, they could pick her out in the crowd. She was simply dressed in a long beige mac and was carrying a large leather bag and an umbrella. The camera followed her along the street, snapped her going in through the door of the cafe and sitting down.

'Is Jennings already there?'

'It's not clear,' Wightman said, clicking through the images.

'I'm sure he was there before her,' Tartaglia said emphatically. 'Look at that one. Even though he's not in the picture, you can tell from the angle of her face as she sits down that she's looking at someone opposite. And she's smiling.'

'Looks like he was waiting for her. No chance meeting.'

'Yes. Which means Jennings lied. He said that the last time he saw her was a week before her death, at college. He also denied ever meeting her anywhere else. Are you sure about the date these were taken?'

'It was the Thursday before her murder.'

'Can you make double sure?'

Wightman clicked on the image, drew down a menu and clicked again. A pop up box appeared. 'There you go. All the info you need. Number of pixels, date and time of photo, date and time it was imported and modified, name of jpeg, size and even the make of camera. Pretty neat, isn't it?'

Wishing he had such fluency with the technology, Tartaglia checked the date and time. The picture had been taken at 15.37 on the Thursday before Watson's murder. 'Thank God for digital. What happens next? You have Watson coming out on her own, don't you?'

'Yes.'

'I want to see where she goes.'

The pictures showed Watson emerging from the cafe and walking down the street. The angle changed as Broadbent crossed the road and followed behind her. The pavement was crowded but in most of the shots they could see the back of her head and shoulders as she walked along.

'There's Jennings,' Tartaglia said, nudging Wightman's sleeve. He pointed at the screen. 'Look, there, the bloke in the green anorak.'

Wightman frowned. 'It's him, isn't it? With the blond hair?'

'Yes. He's right behind her.'

'He's definitely following her. Why didn't Broadbent mention this at the time?'

Tartaglia shrugged, thinking back to what Angela Harper had said. 'Any number of reasons. By all accounts he was very upset and confused when he was first questioned. Maybe he wasn't even aware of what he had caught on film. He's watching Watson. She's his focus. He may not even have noticed Jennings at all.'

As the camera followed Watson down the busy street, Jennings's head was just visible amongst the crowd of people. Watson turned into what Tartaglia recognised as her road, rushing between the traffic across the street, a shopping bag and satchel in her hand. The last few close-up shots showed her climbing the steps to the front door and fumbling in her bag for her keys. As she went inside, Broadbent zoomed out to a panoramic view of the street.

'Can you see Jennings anywhere?

'No. I don't think so.'

'Isn't that him over there, by the bus stop?'

Wightman selected the area and enlarged it.

'Certainly looks like him. He's got his back to the camera. He's staring at Watson's house.'

Tartaglia pushed back his chair and got to his feet. He had seen enough. 'I want you to go through the rest of the photos with a fine-tooth comb and I want a printout of anything that looks remotely interesting, along with a log of the date and time they were taken.'

'It will take a while, Sir.'

'Take as long as you need,' Tartaglia said. Steele would just have to wear the overtime expense. 'If it helps, I could ask Nick to give you a hand...'

Wightman's boyish face cracked into a wide grin. 'I'm better off on my own, Sir. Nick doesn't know his arse from his elbow when it comes to computers.'

'Point taken. When you're done, send the files and a list of the ones we're interested in to the anoraks at Newlands Park. Let's see what they can get out of them.' A good computer-graphics technician could work the most amazing wizardry with a jpeg.

Feeling almost high from the tension, Tartaglia went over to his own desk and dialled Turner's mobile. But there was no answer and he was diverted to voicemail. He slammed the phone down hard in its cradle, causing Wightman to look up questioningly. They had to find Jennings, but there was nothing to be done until he got hold of Turner.

Needing to fill in the time until he heard back from Turner and take his mind off things, Tartaglia said, 'I'm going to get a coffee and stretch my legs. Can I get you something?'

'A large latte would be nice, if you're going out.'

Tartaglia put on his leather jacket and marched down the corridor to Turner's old office on the other side of the building, wondering if he had taken refuge in there. But it was empty, as was the large, open-plan office outside, most of the detectives being either at lunch or out on the road somewhere. Eventually he tracked down a young constable on Turner's team microwaving some soup in the office kitchen and asked her to page Turner immediately and have him call him on his mobile.

Outside the air was cold and damp, the sky heavy with cloud. He walked through the small, crowded car park at the rear of the building and out through the front gate, zipping his jacket up and shoving his hands in his pockets for warmth. Excitement still bubbling, mixed with frustration and irritation at not being able to reach Turner, he strode briskly down Station Road towards the village, wondering just how long it would take for Turner to call him back.

Whilst the photographs showed a previously unknown meeting between Watson and Jennings, somewhere close to where she lived and far from the university where she had taught, they didn't add up to much more than that. To his eyes, it didn't look like a chance meeting, but such things were open to interpretation. There was no record in the files of Jennings calling Watson's phone at any time, although it was possible he had used a payphone. Maybe the meeting in the cafe wasn't the first; maybe she had invited him over for dinner on the Saturday and he had murdered her. But it was pointless speculating. What they had was barely enough to arrest him, let alone take to the CPS. Having coffee with a woman and following her home didn't add up to a watertight charge of murder. He felt as though they were clutching at straws, but it was all they had. Somehow, they had to find proof.

He caught the smell of wood smoke on the air, someone nearby enjoying a proper open fire in contravention of council regulations. A fire was one of the things he liked most about winter, taking him straight back to his childhood home in Edinburgh where his father had insisted on making a log fire every Sunday, in spite of the fact that they had central heating. As he approached the Green, he heard a shriek of high-pitched laughter together with a sudden clamour of quacking and looked across the road. The grass under the trees was almost entirely covered by a thick, sodden brown carpet of leaves, brought down by the recent wind and rain. A woman with a pushchair and a couple of small children about the same age as his nephew and niece stood on the path by the pond. Wrapped up in bright yellow macs and wellingtons, the children were scattering bread to a crowd of ducks, geese and pigeons. Each scrap was being loudly fought over and a couple of geese were trying to steal a march on the others by trying to grab the bread straight from the children's fingers. Judging by the children's laughter, they didn't seem to mind. Looking at them, they seemed so carefree, with all the time in the world, and Tartaglia envied them.

He turned left into the High Street and walked the last few yards to the Food Gallery, a recently opened cafe and delicatessen which served the best sandwiches and coffee for miles around. The morning trade was always brisk and the stools at the counter in the window and to one side of the door were all taken, the occupants busy reading the magazines and daily newspapers provided, as they drank their tea or coffee. Tartaglia edged his way through and joined the back of the small queue, behind a broad-shouldered middle-aged woman in a green tweed coat. Her basket was full to brimming with jars of jam, chutney and mustard from the large dresser display at the back, along with a couple of packs of Thai fishcakes from the freezer. The sight made him feel suddenly hungry. As he studied the blackboard of daily specials, wondering what to have, he heard another woman loudly proclaiming to the owner, Nikki, how the shop's homemade brownies were the best she had ever eaten. He had just decided on bacon, avocado and watercress on rye, with mayonnaise, together with an espresso for himself and a latte for Wightman, when his phone rang. Turner at last.

'Got your message. You'll be pleased to hear I've finally found Jennings.'

'Good. Are you with him now?'

'No. He's been kipping at a flat on Camberwell New Road. He's due back in a couple of hours. You said it was urgent. What's up?'

'We've got enough to arrest him.' Tartaglia briefly told Turner what they had found amongst Broadbent's photographs. 'Where are you?'

'Still at the flat. The girl who has the flat said I could stay until he gets back. But if I'm going to arrest him, I'll need some backup.'

'I'll be there as quick as I can and I'll bring Nick with me.' Although Turner had at last come up trumps in finding Jennings, Tartaglia decided it wasn't wise to leave anything to chance, or to Turner.

'Make sure you keep a low profile,' Turner said, after giving him the address. 'Jennings knows we're looking for him and I don't want him to sniff us out and do a runner.'