“I’m fascinated by it. It’s history.” Lenny Henry is explaining why he has decided to write an autobiography (Who Am I, Again?) about his childhood in Dudley and the beginning of his 45-year comedy career. For Henry, this isn’t just a bit of navel-gazing and the odd anecdote featuring Chris Tarrant (although there is some of that). It is about bearing witness. “I grew up in a period where, just down the road in Smethwick, a Tory politician got in with the slogan ‘If you want a nigger for a neighbour vote Labour’,” he says, referring to Peter Griffiths’ notorious 1964 election win for the Conservatives. “I’m living just down the road from Wolverhampton, where the Rivers of Blood speech was made*. So I’m in a place where there are toxic elements that you think would be an obstacle to my progress in life. But, actually, I think those things are part of what makes us stronger.”

Henry tells me this as we sit in the corner of a lounge bar that looks out over the old BBC Television Centre in west London. The place is decked out in mid-century modern decor, with plush stools and mood lighting. If we were meeting in the evening, you would expect him to order an old fashioned, but it is not even 10am and all he wants is a bit of toast. Henry – who is half incognito in a flat cap, glasses and a polka dot scarf – seems to be on first-name terms with all the staff and politely asks one of them to turn the muzak down a bit. This is very much his domain. “All that used to be offices,” he says, gesturing toward a section of the building that has been turned into luxury flats. “You’d go in there and get your ideas ripped apart.”

Now 61, Henry started his comedy career in 1975, and he has become arguably the UK’s most recognisable comic. But there is a lot the British public don’t know about Henry. In the book, the extent of the racist abuse he received as a young man, not to mention the physical violence at home, is revealed in painful detail. To write it, he looked back into his past, opened up a “pandora’s box” of memories and then began, as he puts it, “to vomit out the chapters”.

The book ranges from his infancy to until he was a few years into his nascent career. It ends before his marriage to fellow comedian Dawn French in 1984; after 25 years together, they divorced in 2010. The pair have a daughter, Billie, who is in her late 20s. Henry is now in a relationship with the theatre producer and casting director Lisa Makin. When we meet, he has just landed from New York and needs to send her what he calls a “yaaaaaay message” to mark the occasion.

The light entertainer: Lenny Henry on New Faces in 1975

These days, Henry isn’t considered a child star, but that is exactly what he was. Aged 16 when he made his TV debut, he arrived on our screens dressed in a wide-lapelled suit with an oversized bow tie and was introduced by Derek Hobson – the host of New Faces – as “a Dudley lad”. His impressions of Stevie Wonder, Muhammad Ali and Frank Spencer were good enough for him to win the talent competition and thrust him into the world of mid-70s light entertainment. Watching the footage now, it is striking how lanky and awkward and yet incredibly confident he was, suggesting years of practice, which in some ways was true.

Throughout Who Am I, Again?, we see Henry using his comedy to ward off bellicose bullies or honing his short impressions sets in sometimes hostile working men’s clubs. He turned the violence he received at the hands of his mother into a live performance that would eventually help him to buy her a home. But his honesty in revealing this in the autobiography caused friction. “My family were very sensitive about it,” admits Henry, who had to work especially hard to convince his four older siblings (he is one of seven) of the merits of publishing a book about their difficult home life. “They all got their manuscripts and they were allowed to express what they felt about it and some of them were a bit weird about chatting about our business in public,” he says. “Some of them said: ‘Go on, say it.’ So I was encouraged by that.”

But despite the positive spin, there is a dark frankness to the book, not just when Henry recalls the racism he faced in his youth but, more so, when discussing his mother, Winifred. He puts the violent beatings she gave him down to her own upbringing. “It’s an inherited violence,” he says. “And, you know, everybody hit their kids back then. Teachers backhanded you in the classroom in front of other kids. You got the stick, the cane, the slipper. Your mum beat you at home with a stick or a shoe. And if something happens enough, it becomes routine. I wasn’t the only one.

“Charlie Chaplin used to say that comedy is tragedy plus time,” he says. “And I think that’s true. Because when you’re an eight-year-old kid and a grownup is beating you, all you’re thinking is: ‘When is this going to stop?’”

Yet Henry clearly revered his mother, who died in 1998. She came to Britain in the second wave of Caribbean immigration in 1957 and settled in the Midlands before having an affair, of which Henry was the result. When Henry was 10, his mother told him he had to go and do chores for his “uncle” Bertie in exchange for pocket money. He helped him every Friday for 18 months until he was told that Bertie was his real father, not Winston, the man he had grown up with. Henry says he was ashamed of the truth for years, but wants to “own” it now. “My story is an immigrant story,” he says. “My story is of people moving from one country thousands of miles away to another and forming new links, new family and new relationships. And that’s just what it is. It’s not illicit, it’s not salacious in any way. It’s a life thing.”

Henry, aged 16, with his mother in January 1975, just after his TV debut. Photograph: Mirrorpix/Getty Images

Incredibly, Henry says it wasn’t the revelation about his biological father or the beatings that caused him to feel anger toward his mother, but rather the moment when she started getting caught up in the circus that began to surround him as his career took off. “I felt that she was buying into the showbiz story and she was changing,” he says. “Why was she changing? This is the woman who, up to five minutes ago, would backhand me or beat me or whatever, and now she’s calling me Lenny instead of Len.”

Some of this anger may stem from the situations that Henry was put in. He wasn’t just on New Faces, Tiswas, the Saturday-morning children’s television programme, and The Fosters, the UK’s first all-black sitcom; he was also on The Black and White Minstrel Show, a decision that was taken by his family and management. Henry didn’t perform in blackface, as some black comedians – such as Bert Williams in the early 1900s – had done, but he was on the same show as acts that would be repulsive to today’s audiences. What does he think of the people who put him in that position? “Of course I have an opinion,” he says. “I probably wouldn’t share it with you. But I do know this: if it’s me, and I’m that person’s parent or guardian, I’m not going to let them be in a minstrel show.”

Henry describes Dudley in the 60s and 70s as a “semi-racist” environment, which seems generous considering the stories recorded in his book. What would be known now as “micro-aggressions” were the best Henry could expect from some of his school friends, who were more likely to beat him up while calling him a “coon” or a “wog” than to touch his hair without asking. Looking back, Henry wishes that he had been more like the Jamaican boys who met racist epithets and violence with fists and bricks of their own. “I wish my dad or somebody had taught me how to fight and defend myself,” he says. “Because you’re very vulnerable if you can’t stick up for yourself. I wish I’d fought back and I think that’s now where all the activism comes from. It’s this thing of speaking your mind and not being scared – and we need to be, because we’re all being embarrassed by a 16-year-old girl from Sweden at the moment.”

Dressed as Theophilus P Wildebeeste in a sketch from the 1988 Lenny Henry Christmas Show. Photograph: Radio Times/Getty Images

But being brave and speaking out wasn’t simple in 1975 for a teenage black British comic. Henry was told by managers and peers that the place for “politics is in your private life – you don’t do politics on stage”. It was advice he heeded until he began to call for the entertainment industry to address the systemic racism that he had seen throughout his career. In 2008, Henry made a hard-hitting speech to the Royal Television Society, slamming broadcasters for not doing more to encourage ethnic diversity. In an interview with the Guardian shortly afterwards, he said: “I do not think the media is racist. I do think that, as an industry, we are stuck in terms of providing a support system for black, Asian and ethnic minorities who don’t have a natural way into the industry. It’s bullshit, it needs to change.” It didn’t. So, in 2014, he was louder still, calling out the industry’s terrible record on diversity in a Bafta lecture. “People aren’t just hitting the glass ceiling: they are standing on a glass precipice,” he said.

Recently, Henry was one of the prominent Britons of colour who wrote to the BBC to complain about the treatment of Naga Munchetty. The corporation had disciplined her, but not her co-host, Dan Walker, after a discussion about Donald Trump’s “go home” comments aimed at black and Muslim US senators. Unsurprisingly, there is a weariness to Henry’s voice at having to be discussing these issues again, after years of activism. “It was so benign, though,” he says of Munchetty’s comments. “I know there are guidelines and you are told to adhere to them. But the thing is, she was on TV with her TV husband having a chat about things. And he asked her how she felt about a certain thing, and she replied, in a benign but truthful way. That was all right. She didn’t kill anybody.”

A decade on from his Royal Television Society speech, Henry seems at a loss as to what can be done to improve equality in the British media and worries about what it might take for change to happen, “not because we’re forced to by another Grenfell or by another Stephen Lawrence or by another Naga Munchetty. Let’s just say we’re going to do something good because we want to do it, not because we were forced to by some terrible event.

“I had 35 years where I’d never have any meetings like this,” he says, pointing at me – a black journalist asking him questions. “Never interviewed by somebody like you. Never in a creative meeting with somebody that looked like you.” There was one moment when he thought things were turning; when he walked into makeup on the set of the mid-70s sitcom The Fosters. “There was a mixed-race head of makeup. And I thought: ‘Oh, OK, things are changing.’ That never happened again. That was an anomaly. I never met a makeup artist of colour for the next 35 years.”

Red nose day: Henry co-founded Comic Relief in 1985. Photograph: Mark Richards/Daily Mail/Rex

Henry is doing his bit to offset some of that imbalance with a new series for Gold – Lenny Henry’s Race Through Comedy – in which he tells the mostly forgotten story of black British comedians such as Charlie Williams, the Doncaster standup and former professional footballer he used to impersonate. He has also been an outspoken critic of the government’s treatment of the Windrush generation, and earlier this year starred in and executive produced Soon Gone, a BBC drama that was, in part, inspired by the scandal, of which he “felt the sting of injustice”.

One place that Henry has been able to make a significant impact is with Comic Relief, the charity he co-founded with Richard Curtis in 1985 in response to famine in Ethiopia. Last year, Comic Relief had its effectiveness called into question. In response to pictures posted on Instagram by the documentary maker Stacey Dooley, Tottenham MP David Lammy wrote: “The world does not need any more white saviours. As I’ve said before, this just perpetuates tired and unhelpful stereotypes.” Lammy added that Comic Relief had “fallen short” of what he called its “public duty” to promote racial equality and serve minority communities.

Surely it must have hurt to have something he has been working on for more than 30 years painted as not only outdated but actually counterproductive? Not so, says Henry. “He wasn’t saying anything that we disagree with. We could have done without it on the day of Comic Relief, but we’ve always been aware of the lack of diversity behind the scenes.”

Henry says he has pushed for more black directors and the use of local film crews when shooting takes place in Africa. But he doesn’t accept that Lammy was criticising Comic Relief alone. “David was commenting about all the broadcast media,” he says. “He just happened to pick on us because Comic Relief was out and the optics – sometimes – aren’t good.

“We are aware of it,” he adds. “And we are changing.” Even if the change is not coming quickly enough for some, it is hard to doubt Henry’s sincerity. “When, in 100 years’ time, we look back at the way things change, we’ll go: ‘Wow, that was a snap of a finger.’ But when you’re in the middle of it, change is long. And I think that’s the problem. Things aren’t happening fast enough.”

• Lenny Henry’s autobiography, Who Am I, Again?, is published by Faber (£20). To buy a copy for £17.60 with free UK p&p for orders over £20, visit guardianbookshop.com or call 0203 176 3837

• An Evening With Lenny Henry is touring the UK until 29 November. For venues and tickets: lennyhenryontour.net

* The Rivers of Blood speech was made in Birmingham by the then MP for Wolverhampton South West, Enoch Powell.