Something struck me for the first time as I looked out of the window of the train we'd taken from London to Edinburgh. Every time we approached a town or city after a happy half-hour spent gliding over greenbelt, I saw houses that looked exactly the same as the one in which I had grown up. Without fail, a wide ribbon of plain brick, small-windowed terraces and semis - all with reinforced glass doors and wood-panelled porches - represented the bleed from rural to urban and back out again.
"Look!" I said to my friend, flinging a hand across her face and pointing at the anonymous terraces. "It looks just like me mom's house!" I'd left home five years earlier, but half a decade's worth of university and extensive travel hadn't ironed the Brummie out of me. It takes leaving a place to discover its significance in shaping your life (and your voice). I realised that, roughly between 1955 and 1970, every city in Britain - not just Birmingham - had transplanted the last vestiges of its poorest urban dwellers from its belly to its outer periphery, on to council estates that all looked exactly the same.
At least, they all seemed to look the same from where I was sitting. It was their very uniformity that alerted me to them. The East End of London, to which I'd moved as a teenager, contained such a higgledy-piggledy mixture of tower blocks, mews and maisonettes that no two walking expeditions - to the shops, the park, the library - ever looked or felt the same. Yet I could take the Tube to Becontree, a town-sized estate for decanted East Enders, built between the wars, and see street after street of identical houses that could almost trick me into thinking that I'd tried to leave home, only for it to follow me south.
Schlepping back and forth from London to Bir mingham (or, more precisely, to its eastern outskirts, beyond the city boundary yet filled with vivid Blues shirts) in visiting my parents, I became more aware with every visit that I was swapping one life for another, if only for a weekend at a time. I would leave my harsh, busy, inner-city estate on Friday and turn up at the spread-out, deserted-seeming estate of my childhood feeling as though I'd left bits of memory in both places.
It was the knowledge I now had of the world outside that threatened to do things to my head whenever I went back. I realised that the estate I had grown up on was a place of containment, and that to get a sense of how truly large one's life could be, I had to leave it. Its planners had won awards for the sympathetic way in which they had tried to break up the uniformity of its 18,000 units, but I dread to think what it would have been like if they hadn't made even that effort. You had only to step beyond the city boundary and on to the estate to know that you'd entered a maze, an island state of self-similar patterns.
The rest of the time, council housing obsessed me to the extent that I made special journeys to estates of historical and architectural interest. Byker Wall in Newcastle, for instance: that didn't look like me mom's house at all, as indeed was the architect Ralph Erskine's intention. On that trip, I discovered that Newcastle has an underground train system. I also found that, despite Erskine's laudably human-scale design, which forms a wall of brick against the dual carriageway and encloses (or isolates?) the estate's residents in a community of car-free walkways and awnings in the sky, he couldn't design out the propensity for the poor and unemployed to migrate to places where there are more jobs.
Byker was less than 30 years old at the time I visited it, but its creeping voids - empty flats shuttered against squatters - suggested that it may one day outgrow its usefulness. Sometimes, when visiting Speke in outer Liverpool or parts of Toxteth and the Dingle, nearer that city's centre, it feels like you could say the same for much of the council housing in the north. Housing-association terraces, distinguishable from Sixties council houses by their dark-brown brick and Brookside-style layout, lie empty five years after being built, as people trudge outwards, towards the suburbs and the south.
Scotland's council housing tells another story again. On that first trip to Edinburgh, I hadn't registered the tower blocks of Leith so much as the tenements that had remained, now refurbished, in the centre of town. A few years later, I took a bus across to Glasgow and gulped at the way it resembled Paris: a Corbusian doughnut city ringed by peripheral high-rise estates. Their names had entered a litany of "notorious council estates" far beyond the border: Easterhouse, Castlemilk, Red Road. In the Gorbals, I saw a big mossy rash where Sir Basil Spence's flats at Queen Elizabeth Square once stood, promising - at least in Spence's head - to resemble an ocean-liner with fluttering sails on washdays.
Back in London last week, I found myself gazing out of the window on another trip, this time on the 65 bus from Kingston to Putney. During improving walks across Richmond Park there was always the sight, on its eastern periphery, of the Alton estate at Roehampton, and the promise to myself that I'd wander over one day and inspect its award-winning mix of modernist high-rise blocks of flats and low-rise terraces.
The 65's route wound itself around the narrow roads of the estate from the softer-edged housing of Alton East to the hard-core Corbusier-worship of Alton West: another island state, marked out by its very visibility as council housing. We didn't have to present passports or open a gate to enter or exit; the houses formed their own sign, which said: there's no such thing as separate but equal. The bus seemed to breathe out as it rejoined the main road.
Lynsey Hanley's "Estates: an intimate history" is just out, published by Granta Books (£12)