I wonder what a passerby would have made of us as we stood on the pavement last Saturday waiting for the unveiling. We were a smallish crowd, maybe 15 in all, with grey predominating in hair and beards. A gold chain shone around the mayor's shoulders; our councillor spoke briskly; the old and distinguished local historian sat in her chair and looked up brightly at people who stooped to talk to her. Then the postman arrived, which pleased everybody because he's a local man, born in the streets he still treads, and his presence gave us the fleeting but not false sense that we really do belong to a community. A passerby might have thought: "There's a bunch of people on one of those London walks. Perhaps they've stopped outside the scene of a famous murder." In fact, I was among what might be called the old Islington middle class, the kind of people who catch buses and use libraries and remember each other from the time their children, long-ago grown up, shared a playgroup; a dwindling class, which may disappear in these parts never to be seen again.

After the speeches someone tugged a cord and the curtains parted to reveal a green plaque announcing that the estate agent's beneath was once the office of James Edmondson, builder and developer, who in the late 19th century built most of the north London suburb we live in, including the row of shops that held his office and now bears the green plaque. "A showy red brick shopping parade," says Pevsner disdainfully of a terrace whose official address, still just visible on its original enamel sign, is the Broadway, Highbury Park.

Edmondson built high streets like this all across north London, and sometimes in south London, too. Other Broadways arose in Golders Green and Winchmore Hill. Muswell Hill had its Station Parade and Royal Parade, Crouch End its Topsfield Parade, Sydenham its Grand Parade. Each was three or four storeys high – flats above and shops below – and made of red brick ornamented with white plasterwork: "developer's baroque" Pevsner calls it. In a remarkably short time – roughly, the 30 years leading to 1914 – developers such as Edmondson had carpeted the fields and hills of north London with housing estates and shopping centres (with an occasional theatre or tennis court thrown in) so that a lane that might have been trodden by a herd of cows in 1880 had tramcars rattling down it by 1910.

Developers grew rich. According to research by Judith Hibbert, Edmondson had modest beginnings as a carpenter's son who helped his father with repairs and modifications to existing buildings. Twenty years later he was so busy with work that a special railway siding was required to unload the 300,000 bricks that were needed every day to build Muswell Hill. Edmondson's houses ranged in price from £500 for the straightforward Highbury terrace to £1,000 for the double-fronted or semi-detached villa in Muswell Hill that might come with a billiard room and electric light. Similar homes could be rented from £50 a year. The profits elevated the Edmondsons up the social scale from their beginnings as jobbing carpenters. James Edmondson retired to Bournemouth; his son was first a Tory MP and then a Tory peer, Baron Sandford. It was a family fortune made from people who wanted their own more modest versions of betterment: airier houses with gardens and room on the top floor for a cheap servant, who would bring home lamb chops and sweet sherry from the shops on the Parade.

Before London became my home, I would see these houses from the Edinburgh train and vow never to live in one. I look back on this earlier edition of myself with interest and alarm: what airs and graces, which fancy-dan ways, made me so sniffy at the thought of living in these late Victorian and Edwardian terraces? Were their square bay windows and privet-hedged front gardens so off-putting? Did it matter that they swept over the north London hills in uniform rows? What was the problem for someone like me who, after all, had grown up with the most ordinary architecture: Scottish local authority domestic, c1930?

There can be only one answer: fashion. Well into the 1970s, the most prized London houses in terms of architectural style were Georgian, with their flat fronts, half-moon fanlights and deep first-floor windows. They didn't come cheap. The bargain days of gentrification were over. Well-paid work on a newspaper might afford a mortgage on a flat in one of them, but couples who earned less or who had children looked further out. In any case, as those who couldn't afford them said, Georgian houses had the disadvantages of narrow staircases and dark basements. The compelling case for renewed interest in the ordinary Victorian street had arrived, and in London was taken up by thousands of people – academics, teachers, public servants, journalists – who wanted somewhere comfortable and sociable to live that was still more city than suburb.

We could hardly be called gentrifiers. The 1901 census shows that our street, completed by Edmondson 10 years before, contained a stockbroker, an actor, a dentist and a picture frame-maker, as well as a dealer in foreign stamps and several kinds of clerk. A bank clerk and a gold engraver and their wives occupied my own house. Half of the 53 households had domestic servants. One family came from Germany and two families from Scotland; otherwise the street was resolutely English, with most residents born in the home counties or elsewhere in the capital.

In some ways – and setting aside the live-in domestic servants – very little has changed. The street is still pretty English and includes a fairly wide range of occupations – journalists, mature students, local government retirees, musicians, lawyers – that reflects the clerk-stamp dealer-actor mix of 100 years before. Out of this mixture in this and adjacent streets has come the conservation society that arranged the plaque, as well as a guerrilla gardener or two and other groups that promote the local interest. We look on them fondly and wonder if in our neighbourhood they may be last of their kind, because no younger version of them could afford to move here now, when a house costs at least a million-and-a-half. Only the monoculture of the City of London provides salaries that would secure a mortgage for that kind of money, though a buyer in Malaysia looking for a safe investment might do a straight cash deal; why not, when they're already buying flats off-plan in Croydon? A report into Islington's future published this month by Cripplegate Foundation concludes that its middle class will slowly disappear, leaving the population polarised between the very wealthy and the poor, with "a youthful transient and childless sector" somewhere in between.

When I looked at the red-brick terraces from the Edinburgh train 40-odd years ago I never imagined I would live in one, or of course that living in one would turn out to be the smartest financial move I ever made. But London was then still a city like other cities – Edinburgh multiplied by 10, maybe, but not so big and singular that it stood outside the drizzling weather of the British economy. Now it threatens to become the world headquarters of speculative house-buying as well as of financial capitalism; the social damage may be immense.