"My mum, the last thing she told me before I left was, 'You're either going to be in prison or you're going to be big.'"
Octavian - who has just got a step closer to the big time after being named winner of BBC Music's Sound of 2019 - is recalling the day, at the age of 14, that he was thrown out of his mother's house.
"She was bare angry at me, so it was weird that she said that," he says. "But I always kept that in my mind.
"I knew I'd be big because I didn't want to be in prison. So I kept myself motivated just through that."
The French-born, London-based musician - full name Octavian Oliver Godji - spent the next few years homeless, jumping from sofa to sofa, trying to keep that dream alive.
He won a scholarship to the Brit School, which taught artists like Adele, Amy Winehouse and FKA Twigs, but eventually dropped out. His argument: "I don't believe you can teach someone to be creative."
The friends he made at Brit School stuck with him, though, helping to produce the beats and visuals on Octavian's melodic, genre-defying mixtapes 22 and Essie World (a reference to his SE London postcode).
His breakthrough came with 2017's Party Here, whose ominous intro unexpectedly gives way to a euphoric chorus, where the 23-year-old promises himself: "You're gonna blow, it's just timing."
He couldn't have been more correct. Weeks later, Drake filmed himself singing Party Here at a Golden Globes after-party. Octavian's phone hasn't stopped ringing since.
Recently signed to Black Butter records (home to Clean Bandit and Rudimental), he's just moved into his first flat and has been working with Diplo and Mura Masa as he prepares his debut album.
Let's go back to the beginning, when people still called you Oliver Godji...
So for everyone who doesn't know, Octavian is actually my full real name. I'm Octavian Oliver Godji but people just assume Oliver is my real name because it sounds "proper".
Do you know where Octavian came from?
I don't - but I Googled it and it's like a Roman emperor, and it means "the eighth child".
When you were growing up, who was the first artist you obsessed over?
Michael Jackson. I think everyone did at one point. Michael Jackson is a big part of my life. He was inhuman, almost.
When did you start writing music?
When I was seven, I used to go to primary school and rap bars on the way home. I never wrote, though, I always used to freestyle with my friends.
You got a scholarship to the Brit School but you left under a cloud. What was the main thing you took away from that experience?
Before the Brit School I thought there was only one conventional way to succeed. When I was there, I learned that being talented and having creativity can make you successful. That changed my whole life. I was like, "What? I'm going to be a rapper!"
So if you didn't go to the Brit School to become a musician, why did you enrol?
I just didn't want to do maths! Can I say that?! Maths, for me, is the worst. I can't do it. It bugs my brain.
So I wanted to do something I was good at, which wasn't acting or music at the time. It was literally just not doing maths. But they accepted me and I did a course called community arts practice, which is basically teaching the underprivileged the arts. It was lit. It was good. I liked it a lot.
In your teenage years, things didn't exactly go to plan. How bad did it get?
It was bad, man. I was on the roads, I had no money. I was so poor that I had £0.00 in my current account. I couldn't even take the bus.
How did you keep going?
I kept the possibility of being successful in my mind. That really got me through some dark times - because I was just looking upwards, do you know what I'm saying?
When your mum threw you out, she said, "You'll either go to prison or be big". How easy would it have been to go the wrong way?
So easy. Without you even wanting to go the wrong way, you either end up selling drugs or doing bad things. It's so easy to get pulled into it. It's like being at a party and someone offering you a drink. It's crazy hard to have the willpower to say "no" and not fit in.
I had to kind of step out and say, "I'm poor and I have no money but I don't want to sell drugs. That's not the life for me. I want to be successful." I wanted to prove everyone wrong.
The first song you uploaded was Mary Jane.
Woah! That was a long time ago.
What age were you?
I was 14. That was when I first started BRIT school and I met my friends. The people that believed in me then are still with me now. So Jordan [Christie], the guy that mixed Mary Jane, actually produced Party Here.
That song obviously kicked things up a level. Did you know you had something special?
It's strange because I'd never written such deep lyrics before. To write lyrics like that, about knowing that I'm going to come out of poverty - then to come out of poverty because of that song, is weird.
What made you write those words?
I was writing a promise to myself.
It's really crazy, you know? I made that song in Jordan's house. I was sofa-surfing there. And two weeks later, I'm getting phone calls talking about money like I've never heard of before.
And then Drake turned up in your timeline, singing the hook.
It was the craziest moment of my life. I really, really root for Drake, so for him to post me and talk about me, and to message me... It's a crazy experience.
Can I ask about the tattoo of an "x" you have under your eye? What does that represent?
The "x" actually represents a new man, a change from the "ex-you", do you know what I'm saying?
When I got my first cheque after being poor for seven years, to now having money and being able to do what I want in life, it's like a new me and a new beginning.
So you're no longer the person who said: "Went back to the teachers just to rub one year's wage in their face" [from the song Gun Fingerz].
Exactly. I didn't want that energy any more, so I changed it, and it worked for me and it helped me.
That's why I changed the name of my last mixtape from Revenge to Spaceman. I was thinking, "I'm not who I used to be. I'm grateful for what I have. I don't want revenge." Spaceman was a good way of saying I'm in a different world, I'm exploring the Universe.
So what will we hear from you in 2019?
A lot of Octavian experimenting and a lot of me going crazy and wild. It's going to be a very loud year for me. Loads of music, loads of visuals, loads of albums.
Loads of albums?
Loads of albums this year! Seven or eight!
You posted a picture with Diplo on Instagram last week. Is that the next thing?
It's not the next thing but it might be the next next thing. There's lots of tunes coming out with completely different vibes - from 80s music, to rap, to trap, to Spanish. My music is weird, man.