When Berwyn sat down to create his 2021 mixtape Demotape/Vega, he was at a nadir. He was living in a “shithole of an apartment” in Romford, Essex, with “some brother Alfred, a very depressed, lonely old man”.

With little funds and no equipment, Berwyn went halves on a computer with a friend, and put his “heart and soul” into making the tape in two weeks using a pair of broken headphones.

Since he didn’t have his immigration papers after moving to the UK aged nine, Berwyn realised he couldn’t register to receive royalties. So he decided to spend one last Christmas with his family and girlfriend and then return to Trinidad. Luckily, fate intervened when a musician friend’s manager heard his music and wanted to represent him – providing he could stay in the UK for a while. From there, everything began to change: Demotape/Vega went on to be nominated for the Mercury prize, and Berwyn’s debut album proper, Who Am I – a gorgeous collection of ruminative R&B and rap – is being released by a major label next week.

I meet Berwyn in a studio in Belsize Park, a well-heeled part of north London. Dripped out in a green-and-yellow Wales Bonner tracksuit, the 28-year-old looks as though he has put the troubles of his earlier years behind him. Yet his album reveals that they still have a strong grip: Who Am I is a searching, unflinching yet hopeful self-portrait which tracks the addiction and mental turmoil that was triggered from his experiences as a black immigrant.

Born Berwyn Du Bois in Diego Martin, Port of Spain, Trinidad and Tobago’s capital, the musician grew up hearing steel pan and soca music from the local Creole population, while its Indo-Caribbean communities played chutney and bhangra.

“It’s the ghetto – there’s lots of alcohol consumption, very little going to work, so music was the backdrop of life,” Berwyn says. He remembers evenings on the porch of his house, where he would watch the sunset while sitting on his father’s lap, listening to Motown and soul records. “Now when I try to write a song with Jonny [Coffer, producer] we come up with these old Otis Redding lines – these melodies, rhythms, chords, they were just sinking into my biology.”

Migrating to England and settling in Romford “was like leaving Mars and entering Pluto. Nothing from yesterday was the same as tomorrow.” He describes a town of “strict racially based regimes and rules: there were some streets you couldn’t go down after 10 o’clock because the skinners would chase you off”. He fought daily with Irish boys who he says singled him out because of his blackness.

In school, he felt like a museum exhibit. He’s quick to note that a lot of it was the innocent curiosity of children, but he remembers that in his first week the most popular child in the school kept repeating a racial slur out loud while the class was reading. Berwyn would laugh along with his classmates, not realising what the slur meant. “It’s only in hindsight I look back and I’m like: Oh, they were mugging man off!”

Berwyn knew that he was an illegal immigrant, but had little understanding of it other than “don’t tell a fucking soul or it will end very badly”. But when he reached his mid-teens, his immigration status started to have an impact. “We’re picking GCSEs, and thinking about the next five years. And there wasn’t an exam I sat in and didn’t look around and think: what is the point?” He picked music GCSE because he “wanted time to fuck around”, but ended up falling in love with it.

After his first music teacher was fired for showing the class The Human Centipede, their replacement “saw that I could sing, that I had a natural music ability, and she tried her best to maintain that”. She would stay with Berwyn late after school so he could work on production software Logic, and on Wednesday evenings took him to a folk club. “She had an inkling of what my home life was like, so she did her best to try to keep me away from that as much as possible.”

That home background was the drug trade: “I used to come home and everything was being weighed out and bagged up.” Perhaps inevitably, he started dealing drugs himself, although he wanted to go to university to study psychology: “I was the first boy in my family to not go to jail before 16, so I wanted to change the narrative a bit.” He stopped attending classes, assuming his university dream was pointless given his immigration status, but he would still sit in the library and copy down psychology books amid deals. “Whenever I get a call, I’ll stop, lick my shot, come back, continue writing.”

Berwyn says that he struggles to remember the period between college and the creation of his mixtape: “It’s a fucking blur now; I’m chopping it up with my therapist to try to get a timeline of events.” He came close to canning his creative aspirations in order to work as a labourer – he’s had stints as a carpenter and electrician. And he had a breakdown and recovered from alcoholism twice, all while living under the burden of his status as an illegal immigrant, suffering he sings about on the album track I’m Drowning.

“They took my purpose, bro,” he says. “They turned me into an animal in the field. I couldn’t even go and see a doctor if my belly was griping. I had to pull my rotten teeth out with my own hands. I’d wake up every morning, meet the sun, realise there was no point leaving the bed, drink a Russian beer, and go back to sleep. And that was simply just from them.” Who is “them”? “Crazy, innit: I don’t know. A table full of dickheads in my mind who probably don’t exist in the real world. It’s a word, bro. I’m so passionately angry at a word!”

The hostile environment for migrants is the source of Berwyn’s most righteous fury. “I’m sitting down watching the news and accepting the idea that I am enemy to the state. I’ve accepted that narrative from being a young child.” He singles out Theresa May in particular: “I’ve never seen leadership fail a group of people, so effortlessly.” He likens the demonising of migrants to the way Margaret Thatcher made the country rally around her during the Falklands war. “[May] made us the Falklands, she made the whole country rally against us. And I felt that: it was inescapable.”

Berwyn’s Mercury prize nomination was a watershed moment – especially after all the previous opportunities he was forced to miss. He recalls the time his performing arts teacher sent him to audition for the part of young Simba in The Lion King. “I read up on the requirements [for the part] and I needed my papers so I had to lie to her and tell her I missed the train.” He didn’t audition for the Brit school for the same reason. His teachers thought he was throwing away his chances and “never forgave me for that shit”.

Since 2021, Berwyn has had a right to remain in Britain, but in September 2023, while performing at Ziggo Dome in Amsterdam with collaborator Fred Again, he was informed that he had to get through the UK border by 11pm or he would not be permitted to re-enter the country. “That was just the other day, and to be honest it really fucked up my mental health, because I’m really trying my hardest.”

To support his right to remain application, Berwyn had to write a letter: “Very politically friendly, and lacking so much honesty.” After the situation in Ziggo Dome, he decided he would write the “real thing” on track Dear Immigration on which he recites: “While you send letters tryna threaten me about arresting me / You give me a stomach ache / You made me feel like a fugitive and a runaway.”

That kind of confrontation and vulnerability has made Berwyn one of the most affecting artists to come out of the UK in recent years. His resilience is striking – but so is his tenderness, and the album feels optimistic. On Neighbours, produced by Fred Again, he sings about how love and devotion has carried him through the very darkest of times.

“The album is about reflection,” he says. “I’m with a partner right now that I’m really in love with, and that gives me a sense of comfort throughout all my hardship.” Berwyn is proud of his album, and he’s happy he can share his music more easily than he once could. “I’m always the first to critique myself – and this time I can say I was outstandingly brilliant.”

• Who Am I is out on 12 July