Umar is the son of Mahmud Kamani, 52, who managed to turn a Manchester market stall into a vast fortune.
He set up Boohoo in 2006 with the intention of selling up-to-date clothes for low prices.
Today, Boohoo has a workforce of 1,415, with teams in Manchester, Burnley, London, New York and Los Angeles.
It is endorsed by celebrities like Little Mix and the cast of TOWIE, and is worth an eye-watering £2.6 billion.
In 2006 Umar started working for the family business as a manager, while attending theatre school.
He went on to study international business at Manchester Metropolitan University, and in 2012 he and his brother Adam co-funded PrettyLittleThing after witnessing the phenomenal success of Boohoo.
Before he founded PrettyLittleThing, Umar Kamani admits he was an amateur boxer and playboy who cared only about partying and chasing women. Now he calls this rather hedonistic lifestyle ‘work’.
One day he’s ‘topping up his vitamin D’ in the infinity pool at the luxury Monastero Santa Rosa Hotel in Italy, where a sea view suite will set you back nearly £3,000 a night.
The next, he’s at the wheel of a Riva yacht cruising along the Amalfi coast before posing on the bonnet of his £264,000 Rolls-Royce Dawn in Beverly Hills.
Or maybe he’d prefer his £300,000 Lamborghini Aventador roadster or the coupe version with personalised number plate. For more rugged trips, he has two Hummers and a £92,000 customised Mercedes G-class.
You’ll find him lunching at Nobu in Malibu, California, in a pair of £450 Gucci slippers, with a gold Rolex on his arm. He hangs out with rapper P Diddy at the Grammys and Kylie Jenner at the Coachella music festival in California. All events are, naturally, recorded on his smartphone, which has a £790 Louis Vuitton cover.
His five-year plan, he says, is ‘to make as much money as possible’ and escape his father’s shadow, admitting that half the reason Mahmud helped him start PrettyLittleThing was to ‘get me on the right track’.
‘I’m a rich man’s son and that’s not what I want to be,’ he says. ‘So yes, I have got something to prove. I want to be the rich man. I want to be the successful person.’
PrettyLittleThing is still very much the junior partner of the Boohoo empire, with sales of £11.2 million last year. But it is expanding fast.
It employs 300 staff and counts singers Miley Cyrus, Rita Ora and Nicki Minaj among its fans.
‘If you’re going to be in competition, I would rather keep it in the family,’ says Umar.