Moroccan-British artist and photographer Hassan Hajjaj has photographed some of the biggest names in music and pop culture – from Madonna, Billie Eilish and Alicia Keys to Cardi B and Lee "Scratch" Perry. Now, 40 of his vibrant "Rock Stars" are on show at Paris's Philharmonie. Hajjaj tells us how he creates his instantly recognisable portraits, blends Moroccan heritage with London street culture – and what happens when a global superstar steps in front of his camera.