he Birkenhead Land Registry's address is Old Market House, Hamilton Square. Sounds almost romantic, doesn't it? I pictured a mellow stone building, Georgian, with perhaps a portico. Wood panelling, maybe, with grey stooped figures shuffling past in a Dickensian hush. Fat chance. Negotiating the one-way system brought me to a modern dark red brick building, seven storeys tall with plenty of windows overlooking breathtaking views of the entrance to the Mersey tunnel.

I found a space in the car park for the Fiesta I'd hired to replace my wrecked Nova and tagged on to a group of women heading for the building. They were having the Monday morning chatter to each other about the weekend, obviously familiar with each other's routines. The leading pair stopped at the entrance to the building and keyed a number into a security lock. The women swept on into the building. One of them held the door open for me. That was when I noticed the sign informing me that the public entrance was at the front of the building. One of the great truisms of our business is that the more security a building has, the easier it is to penetrate. I caught the door and stood uncertainly for a moment. It was tempting to waltz in the back door and have a good wander round, just for the hell of it. But prudence won over my sense of adventure and I reluctantly let the door swing closed. I was too busy to spend a day down the police station explaining why I'd hacked into the Land Registry computer network.

I walked round to the front of the building, distinguishable from the back only by the double doors. I entered a cheerless foyer with a security booth and banks of stainless-steel lift doors. The Scouse security officers were as efficient as if they'd been privatized. Name and purpose of visit, who visiting, where car parked, car registration number. Then they note your arrival time and issue a security pass. If I were a dedicated hacker, I could see half a dozen ways to get my hands on one of their terminals.

Again, I restrained my more piratical instincts and went across the hall to Inquiries. It was like a dentist's waiting room, complete with year-old magazines sitting on a low table. The chairs were the cloth-upholstered sort two grades up from those hideous orange plastic ones you get down the Social Security. Everything was a bit scuffed, as if it was last redecorated before Thatcher came to power. I walked over to a high counter in the corner of the room. It was empty except for a cash register and a computer monitor and keyboard. I craned my neck round to read 'Welcome to the Land Registry Computer System' in amber letters on the black screen.

The sign on the desk said, 'Please ring for attention'. They obviously brought the sign with them from the old building, since it's probably the only thing in the whole place made of wood. It's certainly the only thing made of wood with gilt lettering on it. I rang the bell and waited for a desiccated old man in a frock coat to shuffle through the door.

That'll teach me to make my mind up in advance of the facts. It took less than a minute for a young woman to appear who, frankly, wasn't my idea of a civil servant. For a start, she wouldn't have looked out of place at one of Richard's gigs in her fashionably baggy Aran sweater and jeans. For another, she looked like she enjoyed her work. And she didn't behave as if having to deal with members of the public was a major pain for her. All very novel.

'I wonder if you can help me,' I said. 'My name's Brannigan, Kate Brannigan. I rang last week with a list of addresses that I needed copies of the register for.'

The woman smiled. 'That's right. It was me you spoke to. I've got the copies ready, if you don't mind waiting a minute?'

'Fine,' I said. As she disappeared back through the door, I allowed myself a grim smile of satisfaction. No doubt this was where the wait began. I helped myself to one of the elderly magazines and sat down. I was only one paragraph into the fascinating tale of a soap star's brush with death on the motorway when she returned with a thick bundle of documents.

'Here you are," she announced. 'Seven sets of copies of the register. It's not often we get asked for so many, except by conveyancing experts. And in so many different locations,' she added, obviously fishing.

I dumped the magazine and went back to the counter. 'I suppose it made life a lot more complicated for you when they changed the rules to allow anyone to examine any entry in the register,' I parried.

'I don't know about complicated,' she said. 'But it's made it a lot more interesting. I only ever used to talk to solicitors and their secretaries, and occasionally people who wanted copies of their own entries. Now we get all sorts coming in. Often, they want to check the register on their neighbours' properties because they think they might be in breach of some covenant or other, like no caravans, or no garden bonfires. A right lot of Percy Sugdens, some of them are,' she added with a giggle.

She turned to the cash register. I'd taken the precaution of hitting the hole in the wall with the company cashpoint card, so I wasn't flummoxed by her demand any more than she was by my request for a VAT receipt. I made a mental note to ask Shelley to keep a running total of Ted Barlow's account and to bill him as soon as it went five hundred pounds over the retainer he'd given us. I didn't want us to end up working for nothing if I couldn't clear up the scam fast enough to keep his business afloat.

I picked up my copies of the register entries and squeezed them into the back pocket of my handbag. Then, a thought occurred to me. 'I wonder if you could clear something up for me?' I said.

'If I can, I'd be happy to,' the young woman said, giving me a bright smile that appeared to be completely natural. She obviously wasn't destined to last long in the Civil Service.

'What's the actual process here? And how long does it take between details being sent to you and them being entered into the register? I was thinking particularly of land that's being registered for the first time and has then been split into parcels.' If anyone could help me work out Martin Cheetham's role in the double-sale scam, it had to be the Land Registry.

'Right," she said, dragging the word out into three distinct Scouse syllables. 'What happens is this. Every morning, a Day Listing gets put on the computer. That lists all the title numbers that are the subject of alteration, inquiry, registration or anything else. Once a title number has appeared on the Day Listing, it stays listed until it has been entered into the full register. At any one time there are about 140,000 properties on the Listing, so it takes a little time to get round to them all.'

Suddenly, I began to understand how the Land Registry got its reputation for being as slow as a tortoise on valium. Before they started their computerization, it must have been a nightmare. 'So what sort of time scale are we looking at?' I asked.

'It depends,' she said. 'We've got about half a million records on computer, which has speeded things up a bit, except when the system crashes.'

'So, allowing for that, how long does it take for changes to make their way on to the register?'

'For a change of ownership, we've got it down to about four weeks. A first registration takes about eleven weeks, and for a transfer of part, it's about fifteen weeks,' she said.

Light was beginning to glimmer, very faintly. 'So if someone was registering a piece of land for the first time, then almost immediately registering the division of that land into plots and the sale of those plots, the whole thing could take six months?'

'In theory, yes,' she admitted, looking slightly uncomfortable.

'So if someone tried to sell the same plot twice, they might be able to get away with it?'

She shook her head vehemently. 'Absolutely not. Don't forget, it would be on the Day Listing. As soon as the second purchaser's solicitor instigated a search, they would be told that the file was already active, which would ring alarm bells and put any transaction on hold.'

'I see,' I said, smiling my thanks. 'You've been very helpful.'

'No problem. Any time.' She returned the smile.

I walked back to the car in thoughtful mood. I was pretty convinced now that I knew how Alexis and Chris had been ripped off. The root of the scam lay in the difference between registered and unregistered land. I dredged my memory for all I'd ever learned about land, which wasn't that much, since land comes in the final year of a law-degree course. I suspect that might have been one of the factors in my decision to duck out after my second year. But sometimes, like now, that last year would have come in handy.

The ownership of about a third of the land in the North West of England has never been registered. If you think about it, it's only in relatively recent times that there was any need for registration, when we all became economically and socially mobile, as the academics put it. In the olden days before the Second World War, if you were buying a property or a piece of land, you usually knew the person who was selling it. Probably, they'd been your employer, or had sat in the front pew of the local church all your life. Some form of independent registration only became an issue when you were buying from a stranger and you had no proof of their reputation; they just might not actually own London Bridge, after all. Since the Land Registry really got going in the thirties, most transactions have been registered in what was supposed to be a slow but sure process. Ho, ho.

In practice, before compulsory registration was introduced in the late sixties and seventies, a lot of properties still changed ownership on a handshake and the exchange of a fistful of title deeds for a fistful of readies. And, since those properties haven't changed hands again since then, they're still not registered. This doesn't just apply to farmland that's been in families for generations; there are whole chunks of rented terraced housing in Manchester where ownership has remained the same for thirty or forty years. In terms of the Registry, it just doesn't exist. Frankly, I think it'd be an enormous improvement if it didn't exist in reality either.

Anyway, when someone like Brian Lomax pitches a farmer like Harry Cartwright into selling him a chunk of land, all the paperwork goes off to the Land Registry. And I'm not talking pristine forms and word processor-generated contracts. I'm talking dirty bits of paper covered in spidery writing and sealing wax. When it got to the Land Registry, I now knew, it would go on the Day Listing and be given a provisional title number. When Lomax then split the land into plots and sold them, the buyers' solicitors would carry out searches with the Land Registry to see if Lomax really owned it, and the individual plots would be given a number. So far, all very straight.

What happened next was what had done the damage. Lomax had obviously sold the land twice over in short order. But for the scheme to work, there had to be a crooked solicitor handling the second, moody purchase of the land, a solicitor who wouldn't consult the Land Registry's Day Listing, a solicitor who would lie to his clients about the title to the land. And that solicitor was Martin Cheetham.

The problem, as I saw it, was that it was a lot of risk to take for so small a profit. When the people who had been ripped off realized what had happened, they'd be on to the Law Society with their complaints faster than a speeding bullet. Which might well mean the end of Martin Cheetham's career as a solicitor, and all for a half share of fifty grand. Unless ... I had a horrible thought. What if they hadn't just sold the land twice, but had sold it three or four times over? What if there was a queue of punters who didn't even know yet that they'd been conned? After all, it was only by coincidence that Chris had happened upon the surveyors. If they hadn't been there, Chris, Alexis and all their self-build cronies probably would have handed over the rest of the cash. The mind boggled! I began to wonder if getting Alexis's money back was going to be quite so easy after all. If Lomax and Cheetham had any sense, they'd be planning to do a runner any day now before it all came on top.

And there was very little I could do about it. Apart from anything else, I had to sort out Ted Barlow's problem before he went bankrupt. I pulled into a Happy Eater and ordered a brunch of hash browns, omelette and beans while I studied the register entries for the seven properties which had lost their conservatories. I'd also taken the precaution of dropping by the office to pick up the stuff from Josh and from Rachel Lieberman. Taken together, an interesting picture began to emerge. Unfortunately, it was more like a Jackson Pollock than a David Hockney.

Firstly, all the houses in question had been rented from DKL. All the tenants in question shared their surname with the owners of the house. All the title deeds showed that there was a charge against the property. Unfortunately they didn't tell me how much, although the dates of these existing charges corresponded roughly to the dates the conservatories had been bought, and in all cases the charge was held by the finance company that was a subsidiary of Ted Barlow's bank. Surprise, surprise. Interestingly, Josh's searches had revealed that all the owners had good to excellent credit ratings, which explained why Ted's bank's finance company had been so ready to grant them the remortgages. What it didn't explain was how those remortgages came to be granted to someone other than the owner.

Somehow, the remortgages held the key. What I needed to find out fast was how big they were. If those charges were anything like you'd expect from a one hundred per cent remortgage, then things would begin to fall into place. Bearing in mind that each of the houses had been owned by its present owners for at least four years, then the houses had been bought for significantly less than they were now worth. Given that the mortgages had presumably been paid for at least four years, the amount now outstanding should be considerably less than the current value of the house. I wandered across to the phone-booth and dialled Josh. Luckily I got straight through.

'Just a quickie,' I said. 'How do I find out the amount outstanding on a mortgage?'

'You can't,' he said.

I was overcome with the desire to kick someone.

'Oh shit,' I moaned.

'But I probably can,' he added smugly.

Then I knew I wanted to kick someone, only he wasn't within range.

'As a finance broker I can ring up the charge holder and tell them I have a client who's looking to make a second loan against his property, can they tell me how much their outstanding charge is so that I can check whether there's enough equity left in the property. Is this to do with your conservatory scam?'

'Yes. It's slowly beginning to make sense,' I told him.

'I'll ask Julia to do it this afternoon,' he said.

I decided not to kick him after all. 'She's already got the names and addresses, hasn't she?'

I arranged to call back in the afternoon. I was still cross and frustrated because I didn't fully understand how the con was working. But I did have one thing going for me. Rachel Lieberman had given me the addresses of three other properties that fitted the bill. Looking at the dates on the previous sales that had turned into missing conservatories, the scammers seemed to work a production-line system. They were getting the loans through at the rate of about one a month, so, given that it can take up to three months for the money to come through from finance companies, they must have been working three properties at any given time, each at various stages of the operation. Dear God! They really were serious about this!

It was three weeks since the last one had gone down, so by my reckoning, we were due for another any day now. I had a good idea where, a rough idea when. And I had an excellent idea how to discover exactly what was going on. All it should take was a phone call.