Billie Eilish's brother Finneas O'Connell has revealed the pair came up with their "No Time To Die" on their tour bus.
The "bad guy" hitmaker's sibling and producer has revealed that the Grammy-winning pair were given the "first 20 pages" of the script for the upcoming 007 movie to work with and came up with their demo whilst on tour, before heading to London to get legendary composer Hans Zimmer and Johnny Marr to record the orchestral arrangement and guitars respectively.
Finneas told the latest issue of GQ Hype: "We wrote 'No Time to Die' on a tour bus.
"Specifically, in the bunks of our tour bus.
"We were given the first 20 pages of the script.
"I guess that's up to the point when the song comes in during the movie, right?
"That's how all the Bond films open up.
"So we were able to read the first 20 pages, which was obviously incredible.
"It gave us such a good steer and such insight into where the song would fall, and the tone.
"It makes it easier than having to write the whole song based on the entire movie; or in fact none of the movie.
"So Billie and I wrote the song, recorded the demo, sent it to them and then we finished it in London with Hans Zimmer doing the orchestral arrangements and also Johnny Marr from The Smiths. I mean, James Bond? Hans Zimmer? Johnny Marr? Mind blowing."
Finneas insisted he and Billie - who will be joined by Zimmer and Marr at the BRIT Awards at London's The O2 on Tuesday night (18.02.20) to perform the Bond theme live for the first time - prefer to work in more casual settings such as on the tour bus or in a bedroom.
He explained: "I think it was the clock in, clock out, mentality of those places; this didn't work for us.
"I'm a big believer in the benefit of a home studio.
"You're sitting there and maybe you don't know the next line.
"So you go outside for a second, maybe. Make a sandwich. "Play with the dog. Or watch an episode of 'The Office', whatever.
"And then it clicks, you run back into the room, and you've got it. "It's not like your creativity is on the clock.
"People always seem to make a big deal over where Billie and I wrote the album; like that bedroom is a sacred space or something.
"The whole point is that there was nothing special about it!
"That we could make music anywhere.
"Well, anywhere that's not a professional, rented out studio.
"I think when you're driving your car somewhere, parking and unlocking the studio door, going in and turning all the lights on and firing everything up, sometimes even that much effort, that 20 minutes, you're like, burned out."
Finneas also admitted that he and Billie thought it would be "impossible" to make her debut album, 'When We All Fall Asleep, Where Do We Go?', at first, because of the "harrowing experience" they had working on her debut EP, 'Don't Smile at Me'.
He added: "So that project, the EP, was really kind of a harrowing experience.
"It also made us feel like maybe making an album would be impossible.
"We realised how hard it really is.
"But finally, just by sort of the fact that we got older, we got better at collaborating, and making the album became, well easier.
"We became much more trusting of one another, creatively.
"We were much more articulate with our emotions."