JULIA TANNER and her boyfriend, Matthew Bright, are absolutely delighted with their new lodger, Hans. He is quiet, honest, tidy, pays the rent on time, cleans the bath and even takes care of the cats. His only vice seems to be an enthusiasm for old Star Trek videos. Julia and Matthew feel his price is above rubies, and they should know. Before this paragon of domestic virtue came to live with them in their three-bedroom maisonette in Putney, their experience of lodgers was hell on earth.

'When we moved in three years ago,' says Julia, 'we had to take on a massive mortgage. We're both in our twenties, working in local government, and we knew we'd never do it with our two wages alone. We didn't know the first thing about taking in lodgers, but we thought they'd be good company for us.'

With high hopes the couple joined the ranks of that Nineties phenomenon, the accidental landlords. What could be more natural than to let their spare rooms to friends or boyfriends of friends? First to move in were a couple of young men whom Matthew had met at work. They agreed to share the double room. 'That was our first mistake,' says Julia. 'We soon found ourselves refereeing their constant fights. One of them was clean and tidy while the other turned out to be a total slob.'

While the fastidious half of this odd couple complained about whose turn it was to Hoover the carpet, his room-mate littered it with plates encrusted with ancient food, unwashed saucepans, green furry coffee cups and brittle balls of Kleenex.

'When I remember going into the room to clean up and seeing maggots wriggling about on the carpet, I feel ill,' says Julia. 'Even the cats avoided that room. It must have been the smell.'

The tidy lodger felt even worse. After several weeks he gave up struggling against the mess and moved out. This seemed to depress his former room-mate. He painted the walls in battleship grey, began drinking heavily and would disappear for days at a time. 'One night we were woken up by the sound of him being violently sick in our front garden.'

There was nothing for it but to show him the door. An experimental advertisement in a local shop window brought fresh hope. A nice, quiet female tenant arrived to take his place. 'She was a French girl working as an office receptionist and trying to improve her English,' says Julia. 'She seemed to be exactly the sort of person we had been looking for.'

All was peace and harmony to start with. Then suddenly their shy and self-effacing lodger underwent a bizarre transformation. 'She became a born-again Christian out of the blue. She would come home from her evangelical meetings and quote Bible verses at us while we were trying to watch the telly. I began to dread coming home in the evening,' says Julia.

She also treated them to impromptu hymn-singing sessions and stern moral lectures about living in sin and not attending church. 'After she'd been Bible- bashing us every night for a week, Matthew lost his temper and swore at her. She told him that was a sin, too. It was the end. We threw a party when she left.'

If their first pair of lodgers resembled movie characters from The Odd Couple, and their second an out-take from Single White Female, their domestic drama now took a lurch in the direction of Pacific Heights. With their spare rooms standing empty and no rent coming in to cover the mortgage, things were getting desperate. The next lodger arrived in the nick of time. An apparently mature, charming divorcee in his forties, he had spotted their ad, too.

After a month had elapsed without any problems, Julia began to think they had finally found a winner. 'The first hint of trouble came one Sunday evening when he brought round eight of his friends just as we were going to bed. Next morning we found three of them stretched out on the living-room sofa, fast asleep. Then we started getting phone calls from all his pals at midnight and all through the night.'

Profuse apologies followed, but it was not long before the new tenant's charm began to wear off. He kept them waiting ever longer for the rent, which caused anxiety and frayed nerves.

The bad atmosphere was building to a climax. 'I couldn't believe my ears one night when I overheard him telling a friend he had no intention of ever paying me again,' says Julia. 'When I confronted him, he threatened to leave on the spot.'

Instead of making a dramatic exit, however, he turned nasty. 'He began shouting and screaming abuse at me. I lost my temper, too, and we soon had a real showdown on our hands.'

As the scene descended into black comedy, the fisticuffs began. Julia panicked, grabbed a nearby hockey stick and lashed out, and Matthew stepped between them to prevent bloodshed. 'It might sound funny now,' says Julia, 'but at the time it was terrifying.'

This lodger took his front-door key with him when he moved out and left no forwarding address. All the locks had to be changed to be on the safe side. For months afterwards, Julia and her neighbours would run into him hanging around in the street outside, hoping to pick up his mail or muttering vague threats.

By this time, she and Matthew had begun to wonder if they were doomed to a stream of nightmarish lodgers. It has taken the virtuous Hans, a friend of a more reliable friend, to restore their faith in human nature. 'Until Hans arrived, I was beginning to wonder if we somehow attracted these tenants from hell,' admits Julia. 'We have certainly learnt some lessons about screening applicants and setting house rules.

'Ideally, we'd like to be able to manage here on our own or move into a smaller place. But we have a negative equity problem. Until property prices pick up, we know we'll have to stay put. Privacy is still a luxury we can't afford.'