Damian Barr can make you laugh when he's talking about sad things. His father's initial reaction to the news that he was gay, for example, sounds funny when he tells it. "He just said, 'It's not true,' " says Barr, mimicking his father's terse delivery. " 'We don't have to talk about it. It's not true.' Total denial. I said, 'It is true.' He said, 'No. It's not true. We'll talk about it again in a few years.' I said, 'All right, then.' " Barr laughs. I laugh. Then I realise that Barr is laughing sadly, and I feel guilty.

There are many moments in Barr's memoir that operate like this. (His father has since been very supportive.) Maggie & Me is a deeply sad book about a child abused for being different while living in a poverty-stricken, alcohol-damaged Scottish household. It's also a funny account of a child inspired by Margaret Thatcher. Misery memoirs don't usually feature funny bits or Margaret Thatcher as a role model.

“It’s not about rehabilitating Thatcher,” says Barr. “But I wanted to be honest about what she looked like to me: her destructive power but also the weirdly inspiring aspect of her. She was saying things that made sense to me about work and self-determination . . .

“We were really poor, and I didn’t want to be poor. On a very basic level she wanted people to want more. And I wanted more. I don’t think there’s anything wrong with wanting more. What’s wrong is wanting more at the expense of others. I only came to understand that later.”

Barr is actually pretty left-wing, and although Thatcher inspired the young Damian, older Damian knows that Thatcherism was destroying the steel-working community around him. He recalls “the loss of jobs, the loss of routine, the rise of cheap alcohol, that horrible crushing culture of masculinity where you had all these men who suddenly felt they were failures . . . There were lots of angry, depressed men, lots of anxious women and lots of children not knowing what to do.”

Was it difficult to relive the things that happened to his family? “There’s this dramatic irony that happens when there’s the child you on the page and he doesn’t know what’s about to happen and you have to make it happen again,” he says. “It’s horrible. It feels weirdly abusive, and you want not to do it. I put off writing certain scenes for quite a long time, because I thought, I actually can’t face doing this. There were days where I sat and cried while I was writing.”

Brain haemorrhage
He writes heartbreakingly matter-of-factly about ringing 999 when fights broke out in his childhood home and how he fantasised about his granny or Thatcher coming to witness it all. But he also found himself sympathising with his mother more than he expected.

“I thought, You lost a child, then your marriage broke up and you got together with somebody that you thought would be good, because nobody thinks they’re getting together with somebody bad, and then you nearly die” – she had a brain haemorrhage – “come back and discover that he’s been abusing your children,” he says. “No wonder she started drinking.”

Barr’s life was complicated enough without also being gay in a homophobic society. “The red tops were talking about how evil gay people were and how they all had Aids. And there were all these terms like ‘flamboyant bachelor’, and you’d go, ‘There’s something in there. What is it?’ You’d try to decode these words. ‘Is that person like me?’ I felt completely doomed as a child, and I felt Aids was the particular form my doom was going to take. I thought that I would spontaneously generate Aids by being gay. It felt completely hopeless and terrifying.

"So then my priority was not to give it to my family, and I became obsessive about not sharing toothbrushes. I went to see Philadelphia and I thought, That's me, I'm going to die, that's my life. It was really bleak."

He likes the way things have changed. “Equal marriage makes a huge impact, because people see gay people being allowed to be happy,” he says. “And these events involve families – and not just families but caterers and florists and hotels. And all these people are forced to accept that here are two people who are in love and want to build a family together . . . But I’m not complacent. Progress can falter, and rights can be taken away, and people can be repressed again very easily.”

One place where progress has faltered is in the realm of income inequality. Barr sometimes worries about the way middle-class people read Maggie & Me. He loves Shameless, the television drama, "particularly the early Shameless, but the way some people watch those shows, clutching their pearls and going, 'Oh my God, there are poor people!' . . . There have been a couple of times where I've done events and I've actually said, 'I can see you being horrified that people lived like this and titillated by it, but it's actually my life.' Also, it's still going on. It's not historical."

Strivers and skivers
He is, definitively, not a Thatcherite. He laments the disappearance of free education, the rise of payday loans, the Victorian rhetoric of "strivers and skivers" and the myth of the self-made man. "Nobody does it all on their own," he says. "To take all the credit is so self-aggrandising. It appeals to some basic narrative need of people to believe in the hero, but the message 'I've done it and you can too – and if you've not done it it's a failure in you,' that's not true and it's not fair."

Barr benefited from "the kindness of teachers", from television – he wanted to be a journalist partly because of Jennifer from Hart to Hart – and from literature. "The library was like a travel agent," he says. "I genuinely escaped there." He also had the help of a mysterious benefactor, who gave him money for college. He never found out the person's identity. That's a bit Dickensian, I say. "I never made the Pip connection until a friend read it and said, 'It's just like Great Expectations.' "

It's a very strange thing to happen, though, isn't it? "Is it?" he asks. "I suppose it is. It is strange. But I also had strangely random bad things happen, so I'm open to the idea that it was just a balancing gesture. My Granny Mac used to say, 'What's fur ye doesn't go by ye.' "

Nowadays Barr lives in Brighton, a place he heard of first in the context of the bombing of the Grand Hotel during the Conservative Party conference in 1984 and later as a place where "gays with Aids and lefties" lived. He runs a lauded event in London called the Literary Salon. The last one featured the broadcaster Kirsty Wark, the novelist Patrick Gale and Barr's hero, Armistead Maupin, author of Tales of the City. Maupin said, referring to Barr, " 'If I can take any credit for this person . . ." "I was like, 'Waaa'," says Barr, "and we were both bawling. It was a proper love-in." He has also set up a scholarship for LGBT students in need and is writing a television adaptation of Maggie & Me.

The Thatcher footage might be a bit expensive. Each chapter of the book begins with a quote from the politician, and there was a charge for each one. “Oh God, they cost thousands,” Barr says. “Even beyond the grave she’s still making money from herself. I remember thinking, Of course I have to pay; why would I not have to pay?” He laughs. “That’s Thatcher.”

Maggie & Me is published by Bloomsbury