Barney is a girl's best friend: He doesn't make passes or criticise your driving - but you feel safe with him. Martin Whittaker meets the ideal male passenger

Driving around Cambridge, Zillah Loewe admits that she often chats to the inflatable man with the rubber face sat next to her. 'It's good to talk to him. It all adds to the sense of realism. I turn my head to him when I'm slowing down, to make it look as though I have a real passenger in here. I believe that if you feel there's somebody here with you, it's going to look like there's somebody here.'

Officially, Zillah's inflatable friend is called Auto- Mate. She prefers the nickname Barney. He is her own invention and has been four years in the making. So far he has cost 31-year-old Zillah and Brenda Clifford, her mother and business partner, pounds 12,000. So convinced are they of Barney's potential that earlier this year Zillah gave up her job as a restaurant manager to work on him full time.

The result is a fully-inflatable male torso, which packs into a briefcase. Once inside the car, you open the case on the passenger seat, plug him into the lighter socket, flick a switch and in 30 seconds, bingo] A fully inflated hunk, complete with polo neck shirt and jacket - a deterrent, Zillah believes, to any would-be attackers or intimidators.

Her invention is aimed mainly at women, especially professional women who travel alone and feel vulnerable. The idea is rooted in personal experience: in November 1989 Zillah had been helping to organise catering at a wedding in a village near Cambridge. She was driving home alone at 9.30pm when she noticed a car behind her.

'They'd been flashing their headlights at me,' she says. 'I stopped at a give way sign and they pulled up alongside me on the wrong side of the road. Initially, I thought it must be somebody I knew. I looked round and saw two youths leering at me, making obscene gestures and laughing.

'I carried on driving. Perhaps they'd mistaken me for someone else, I thought. Then they started chasing me. I didn't know whether to slam on the brakes, or just leg it. So I put my foot down.

'We were on a very narrow, twisting road. They were coming up as if they were going to overtake, then dropping back. They kept flashing their headlights at me. I was terrified. I didn't know these people. Why were they doing this? I had 10 million things running through my head.

'This lasted for about 10 minutes, going at speeds of up to 70 miles an hour. In a way it was lucky the road was so narrow. God knows what would have happened if they had been able to overtake me.

'I saw some houses further ahead with lights on. I pulled into the driveway and started beeping my horn. The youths stopped for a few seconds, then sped off. It still makes me angry just thinking about it, but at least something good has come of it.

'I thought this is totally unreasonable. I have a car. I want to go out on my own. Anyone should be able to go out in a car - that's your protection. But suddenly, the fact that you are in that car on your own makes you a potential victim. From then on I always wanted to take people with me when I went out in the car. I'd try not to go out on my own at night. I got a mobile phone, always kept a spare can of petrol in the car, and joined the RAC.

'I talked to friends, girls who felt vulnerable. One said she took a torch and rape alarm whenever she went out. I realised it was like going into a combat zone. Then I thought the ideal situation would be an instant passenger you'd only have there when you felt vulnerable.'

As she talked it through with her mother, the seed of an idea began to grow. 'One thing led to another. Mum started talking about having a stuffed jacket, or a dressmaker's doll.

'I said, don't be silly - where am I going to keep it? Keep it in the boot, she said. Then we thought, wouldn't it be a good idea to have an inflatable one you keep in the glove compartment?'

At first, the idea was just to have a dummy for personal use. But the more they talked, the more they realised it had market potential, so they took the idea to a patenting agent.

'We were told you can't patent a blow-up doll. We got the inevitable sex shop jokes. But when I took the drawings for the agent to see, they began to take it seriously.'

The patent applied for, Zillah began trying to work out how to make the product. She and her mother began bringing home bits and pieces - joke-shop masks, wigs and false limbs. 'This place looked like an abbatoir,' she recalls, gesturing around her mother's flat.

They tried making their own masks, after calling the local puppeteers Spitting Image for advice. Initially, Zillah persuaded her boyfriend, Richard, a 43-year-old bodyguard, to model for the face. But the mask went wrong when she misread the instructions and accidentally ripped off half Richard's beard as she pulled away the cast.

The first prototype consisted of an adapted airbed hidden inside a tweed jacket, topped by a polystyrene head complete with wig and dark glasses. On completion, Zillah almost gave up. 'We'd agreed it had to be realistic. But this thing looked like something made in first-year art class.'

However, when she took it out for a trial spin, other drivers and pedestrians hardly gave the dummy a second glance. That was exactly what Zillah wanted. 'We didn't want something that looked like Richard Gere or Hugh Grant. We wanted him to blend into the background.'

Next they had to tackle the mechanical side. They needed an electric pump, small enough to fit into the case. Finally they found one designed to pump up airbeds.

By March this year, Barney was more or less complete. Two months later, Zillah and Brenda packed him in his briefcase and headed for the Great British Innovation and Inventions Fair at the National Exhibition Centre, Birmingham. They were staggered by the response.

'We were very doubtful before we went up there,' says Zillah. 'We thought, everybody's going to think we're mad sitting there with a blow- up doll. They aren't going to understand what it is.

'But people came up and said they thought it was a brilliant idea. Thames Valley Police said they would definitely push it when it was up and running. People from the motoring organisations said the fact that you don't have to get out of the car to use it was an excellent idea.'

Now Zillah and Brenda are about to launch Barney commercially. They plan to make him available with different skin tones and hair styles. He may not yet have passed the acid test of scaring off a car load of thugs or potential attacker. But, says Zillah, he's certainly good company.

'It's a bit like when seat belts became compulsory. It seemed strange at first, but after a while you forgot you had it on. I'm so used to having him with me now, it's become second nature. And he definitely makes me feel safe.'

(Photographs omitted)