'I'm doing a survey in this road to find out how many people would be interested in having our security force patrol your area,' he says, ID badge and clipboard to the fore.
The badge says 'Director', and the list of house numbers on the clipboard is, as I see, filling up with ticks and crosses. He seems plausible enough - neat, young, nicely dressed; and though I'm aware that he is watching me carefully, he is polite, even deferential, and engagingly friendly.
'We'd have a car going down this road every half an hour. All our people are ex-police or military. Lots of firms don't have that,' he says. 'We can make citizen's arrests and we summon the police straight away if we see anything suspicious.'
Somehow I'm doubtful. I wonder who else has shown an interest, but he's evasive, though he does say they can go ahead with only 40 per cent support.
'The lady down there' - he gestures vaguely - 'was telling me she's been broken into twice recently.' Whether this is true or not, I've heard of several break-ins in our road over the past year, and people are worried. He agrees. 'It's sad, isn't it, that the police just can't cope. And people are thinking, is it going to be me next?'
Home alone with children, the thought that it might be me next is distinctly unpleasant. He gives me a leaflet. 'It costs pounds 5 a month. Of course you'll want time to think about it. I'll call back on Saturday.'
My mother, who lives by herself in a tougher part of the city, recently listened for two hours at dead of night as thieves ransacked the ground floor of her house. As I mutter my doubts, she weighs in robustly. 'I think it's excellent. A proper security guard - don't tell me that wouldn't be a deterrent. Who'd break in here with a patrol car going up and down? And when did you last see a policeman in this road?'
'I can't see many of the neighbours going for it,' I say.
'Why not?' she says scornfully. 'Let them have a real crime here, with someone really hurt, in their home - then they'd change their tune.'
Karen across the road agrees the police are thin on the ground. A few nights ago she saw a man trying to wrench off a window next door with a screwdriver. 'So I ran out - I know it was the wrong thing to do - and shouted; anyway, he ran off. I called the police. It took them 20 minutes to get here.'
But most people seem reluctant about to this new form of civil protection. 'I said to him,' says Jane, ' 'If I have a break-in, and you're in the next street and you don't see it happen, do I get my money back?' ' Alice is firm: 'I leave that kind of thing to the police.' But she doesn't have a baby in the house.
I'm more worried about being under the surveillance of strangers. They will have detailed information about our movements and property; and who's to say they'll keep it to themselves? And what would it do for street solidarity? The last time a burglar alarm went off here, doors opened up and down the road and we checked the house: all was well. When a stranger who came to buy a used carpet from us helped herself to a new tarpaulin lying folded in the front garden, we didn't see her do it; Mike across the way did. We traced the woman and she brought it back the next day. Our neighbourhood does watch, and it can be effective. But with a paid patrol in place, would anyone bother?
Come Saturday, I hand over my pounds 5 with misgivings. 'We'll start on Monday,' he promises. Monday, Tuesday pass with no trace of the security patrols. I find a moment to call on Bill next door, who runs our Neighbourhood Watch. He spent 20 minutes interviewing the security entrepreneurs in his front room, and he is not happy at all.
'If we're going to be parting with money, we need to know who these people are. I've asked them for references and credentials. They shouldn't just go round canvassing and taking money from people at the door. I know the police don't really have the resources to cover everything now. But why shouldn't we have a properly funded police service, and pay for it through more income tax?'
Saturday again, and still no sign of the new force. However, my husband comes home from his business trip, leaving a shiny new hire car outside the house. At 10 o'clock that night the doorbell rings. It's Paul and Karen from across the road. 'The white Cavalier - is it yours?' We go out in our dressing gowns and there it is: both front doors wrenched back, glittering glass crumbs strewn across the pavement. We had not heard a thing.
While someone else phones the police, I pad round to Bill's in my slippers; he surveys the damage, angrily. Apparently the same thing happened recently farther down the road. 'Never buy a new car,' he says. 'It's not worth it.' Since car, and indeed radio, are still with us, the desk sergeant on the phone at the police station concludes that the thieves were probably disturbed. We don't know who by, but we are grateful. I fish out my receipt from the security firm, which promises patrols within 10 days but, I now notice, is undated.
It is now three weeks since I paid my pounds 5 to the young man with the clipboard. It added nothing to our security. But we continue to watch out for each other. There are some things money can't buy.