Taylor Swift and Imogen Heap made the 2014 tune 'Clean' within one day.

The Grammy winner, 35, and the British electro-pop artist, 47, teamed up on the track from her '1989' LP and Imogen was also involved the 2023 re-recorded 'Clean (Taylor's Version)' for '1989 (Taylor's Version)'.

In a new interview with PEOPLE, Imogen has recalled how swiftly the pair penned, recorded and produced 'Clean'.

She recounted: "She had an idea on her phone, she played it to me, and I was like, 'That's good. Should we go and record it?' She was like, 'Well....' I was like, 'Yeah, down in the studio, let's just go there now.' So we're like,'Okay.' We went downstairs, we had our cup of tea by the fire, and she wrote the next verse. I started to make music around us. And then by the time she left, which was like just after dinner, we had managed to write the song, produce the song, record the song, chat, meet, have tea, sit by the fire, eat lunch, eat dinner, do an entire record all by ourselves."

The following day, the 'Shake It Off' hitmaker had a concert at London's The O2 arena.

Imogen has revealed that Taylor was the first person to properly interact with her bump when she was pregnant with her daughter, Scout, who was born in November 2014.

She shared: "The other only time I've met her was just a show in Lisbon, Portugal. I went to take my daughter. Scout was in my tummy. Anyway, Scout was on her one-day journey as a fertilised egg, and I didn't know at the time, but that was the day I wrote that song with Taylor. And then 10 years later, the next time I met her, the one and only other time I met Taylor, was with Scout, who was 10 years old, and she knew the story. She was the first other human to interact with me as a pregnant woman. So yeah, it was pretty cool."

When asked what's so special about Taylor, Imogen said she is "extremely efficient" in the studio and knows exactly "what she wants".

Heap shared: "I don't know if there's any secrets. I mean, she knows what she wants, and I pretty much feel she's probably always known what she wants. She is extremely efficient. I've never done that from start to finish with anyone. And I felt very excited. I really appreciated her. There was one moment when I was trying out something a bit different for the middle section, and I was like, 'What about these chords?' Thinking that's just so different. And she was like, 'You know what? I think we're going to lose them here, so let's just do this.' I'm like, 'Okay, that's fine.' What I learned, I suppose, [is] just she's very good in the studio, and she knows what works."