"It was definitely a hit operation," Chrisp laughs. "It was a bit [unreal]."
But Thomas says confidence is key: "You're not going to get shot or arrested ... So we were just like: we may as well.
"The whole thing unfolded in about five seconds. He wound down the window and I threw the USB stick in and yeah, six months later he played it on [BBC] Radio 1."
An impressive feat, considering they started out by playing in primary school bands with no knowledge of instruments, chords or lyrics.
They skipped music lessons and "just made a band". They played indie-punk and wrote songs about not being able to put names to faces.
It wasn't until the age of 13 or 14 that their musical tastes changed to electronic and hip-hop and they started making their own tracks.
They're the first to admit their early stuff "was not that good", but they've been at it ever since, spending the last two years cultivating their five-track EP, Lunch With Bianca.
"We wanted to make the EP to be like sitting down for lunch with Bianca and getting to know her," says Thomas.
But Bianca doesn't actually exist - "She's that person that everyone has in their lives. She's like the female protagonist in a film that we wrote, you know?" says Chrisp.
The EP's already got a great start, after Zane Lowe debuted one of the songs, South Central, featuring LA rapper Duckwrth, on Beats 1 on Wednesday morning.