In a quiet corner of North London in the early 2000s, a teenager with dreams of becoming a singer was scribbling away in her bedroom as albums by Mariah Carey, Eminem, Prince and Amy Winehouse blared from her CD player. Their plastic cases were piled high beside her.

Jess Glynne would transcribe the lyrics to her favourite tracks and then repurpose the melodies to write her own fledgling songs. A reluctant performer back then, she won praise for a rendition ...