The singer, 29, first walked the red carpet at the launch, hosted at Harvey Nichols in Knightsbridge.
She gave one fan a makeover before the event kicked off, with guests including fellow music stars Tallia Storm and FKA Twigs. Later Rihanna, who wore a lilac dress, turned her hand to DJing.
Across town Pixie Geldof and Daisy Lowe, below, were at the Camden Roundhouse as Tommy Hilfiger unveiled the latest TommyNow collection.
Model Gigi Hadid, who codesigned the range — her third for the brand — was the first to take to the catwalk wearing a floor-length tartan coat and denim cut-off shorts.
The show ended with high-wire circus acts and US pop duo The Chainsmokers.
Growing up, I was surrounded by punks and New Romantics, but I’ve always worn the clothes I wanted to wear, which back then were pedal pushers, bright-blue eyeliner and frilly shirts. Nowadays I have more of a rock-chick look – I live in jeans and T-shirts and shop mainly on the high street at H&M, Primark and New Look.
At 5ft and a size 8-10, I can wear children’s clothes. Sometimes the assistants look at me strangely – I remember one being very bemused when I told him I couldn’t decide whether I was age 7-8 or 9-10 in their boys’ section! Being age-appropriate doesn’t ever come into my style choices. Sometimes I look at what other women my age are wearing and think: ‘I would never feel old enough to wear that.’ I call those monstrosities with elasticated waists Werther’s Original trousers – the sort of thing you wear as you’re sucking on your boiled sweet and watching Countdown.