By day, Geoffrey Beattie analysed language, by night he listened to the sounds of Sheffield lives put on hold by Thatcherite economics

I had only just moved to Sheffield as an academic when Mrs Thatcher came to power. As a lecturer in psychology at Sheffield University, I analysed her behaviour in political interviews. I analysed how she took turns in interviews and how she often talked over her interviewer. In an article published in the journal Nature, I identified her distinctive vocal characteristics, including her fast falling intonation pattern, which invited the interviewer in, and I described how she talked over unwanted "interruptions". The Iron Lady was born in our living rooms: a conviction politician who stood no nonsense.

I also started observing my street in Sheffield as Thatcher's rhetoric and policies started to bite. The changes were sometimes quite dramatic. One day the man two doors down worked in the steel industry, the next day he didn't. One month the street was busy with an early morning rush, the next month it wasn't.

Summer came to Netherfield Road, and the mist lifted from Rivelin Valley so that you could see the grey slab flats of Stannington. Steel City was heating up after a year of wind and rain. But Netherfield Road was different that summer. The noises were different. The feeling was different. People got up later. There was no bustle. It was now a street of people who did not work. Some were retired, some hadn't got a job yet; but most had been made redundant. People were bitter. Casual enquiries about work or job prospects could hurl you into a spiral of accusation and complaint: "Thatcher", "Foreign steel", "Bloody recession.'' The pattern of life in the street was transformed. For a few summer months, everything seemed almost OK. But you could have touched the despair in some when summer turned to autumn and then to winter. I tried to capture that as well. I wrote about one marathon runner developing asthma when he was made redundant. He could not even walk any real distance any longer. This was what unemployment did to people.

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There were still opportunities for those who were prepared to get on their bike, we were told. I travelled around the North, writing about some of these golden opportunities.

Dave Cowley from Grimsby was working on a building site in London. Early one morning, I went to work with him. It was a quarter past three. Snow was falling heavily and the wind from the North Sea whipped it right across the road. Dave opened the front door of his little semi, the wind blasted him in the face. "Bloody hell," he said. He'd left his wife in bed,in the middle of her eight-hour sleep cycle. He was in the middle of his sleep cycle too, but he pushed out through the blizzard and into his mini-van. The temperature was way below freezing.

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Luckily the van started first time. But the snow was starting to lie. "That's all I bloody need," he said, as we roared off. "I'll have to push it a bit now or I'll get caught up in the traffic as I get near London." When we got to London, he started work for the day, I slept all the way on the train back to Sheffield.

Meanwhile, others were listening to Thatcher's rhetoric about our economic salvation. For a while, everyone wanted to be an entrepreneur. Mike was a body builder who had served time for robbing a butcher's shop. In the mid-1980s, he got into the kiss-a-gram business. "For 25 quid, I strip off and give the birds a kiss on the cheek. It's easy money. Multiply that by ten and we're talking good money every night."

I tried to help out by taking photographs of Mike in the local YMCA, bench-pressing a routine 380 pounds. I met him a few nights later in an underground car park. Mike didn't like the photographs that I'd taken. He ripped them to pieces. Mike was on a very short fuse. I apologised for taking such unflattering photographs, even though I had thought they were quite good. He asked if I was trying to damage his business opportunities.

Mike never made it as an entrepreneur, but some did. I watched some jewellery salesman who visited clients with a credit collection company. "We're providing a social service to the public," said Brian. "We sell directly to some disabled customer who can't get out to the shops." The interest rate was extortionate. A customer buying a Pounds 300 ring over 120 weeks would pay Pounds 204 on top of that for credit, and these were clients on low income and already in debt. But Brian told me that the customers cared little about the interest rate. "All they're interested in is how much it will cost them a week. We always say in this game that we leave all multiplication up to the customer." These were some of Thatcher's entrepreneurs, making it big in hard times. "I've been to houses where I wouldn't crap in the bog," said Brian, telling me a little bit more about what he thought of some of his customers.

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So there I was, living in two societies. By day an academic analysing language, by night something very different, hearing the schemes and witnessing the lives put on hold by the great de-industrialisation of the North, which started in the early 1980s and rumbled on. I met Alan, who was stony-broke but drove an old Roller to impress the girls. It did the trick for a while; he was Rolls-Royce Alan. I went to night-clubs with Alan where he got in free with his VIP pass, which he got because of the car.

The VIPs always stayed behind drinking after hours. Don fetched the drinks. "Put your money away, it's after hours," he would say. Requests were put to Don. "Play 'Come on big 'un'." It was a tape from the club's security video camera, without sound. One lone punter in a white shirt stood outside the front door. He had blond permed hair. The film was old, a classic. Don provided the soundtrack. He said the words that he claimed the people in the film were saying:

"Go on big 'un, let us in."

"No, you're barred."

"Go on, big 'un."

"Look, I've told you once. Clear off."

It went on and on. Don was very practised at overlaying the soundtrack. "It's authentic," he would claim. It was a boring film I was thinking, until "boom", the big 'un landed a left hook right around the door of the club on the chin of the punter. Down the punter went, like a sack of spuds.Everybody laughed. Then the friend of the man with the perm came to drag him away.

This was the kind of VIP evening waiting for those who made it. But there were stories, some more improbable than you might imagine, behind every one of those faces lit up by the TV screen in the corner, where the big 'un went through his paces again and again on request.

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When Friedrich Engels wrote the preface to the original German edition of The Condition of the Working Class in England in 1845, he wrote "Working Men! To you I dedicate a work, in which I have tried to lay before my countrymen a faithful picture of your condition, of your sufferings and struggles, of your hopes and prospects. I have lived long enough amidst you to know something about your circumstances." I would have loved to preface my work with these words. But life was constantly changing in the North under the Conservatives. There was no fixed picture of the condition of the working class, just a series of images from different angles and a multitude of self-constructions in hard and unpredictable times as we all changed. For ever.

Of course, we live in different times now. Nobody believes that Alan is a millionaire any more. So he has paid good money to meet girls from Eastern Europe. He rang one last week and mentioned his Rolls-Royce. "My hobbies are cooking, sewing and ****ing," she said in reply. Mike, the body builder, came off steroids and the 'roid rage left him, but the stripping business crumpled. Too much undercutting in the stripping business, it seems. He's become a bit of a cynic, doesn't believe what the politicians say any more - like a lot of the people I talked to. They all learned something the hard way.

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Geoffrey Beattie is professor of psychology at the University of Manchester and author of Hard Lines: Voices from Deep within a Recession, published in May, Manchester University Press, Pounds 9.50.