Retailer ASOS confirmed one of the "worst kept secrets" in retailing with the boardroom appointment of former M-amp;S director Kate Bostock.
Described as one of the most influential women in UK fashion, Ms Bostock will be executive director for product and trading from January.
She said she was "very excited" to be joining the online retailer, which was launched in 2000 and now has more than five million active customers and annual sales of around £500m.
Ms Bostock, who is the former head of general merchandise at M-amp;S, said: "ASOS is a phenomenon and I'm in awe of the story.
"With its unique mix of own label and fashion forward brands delivered online and increasingly through mobile, the potential for ASOS globally is huge."
Ms Bostock has also held senior roles at George at Asda and Next.
Her departure from M-amp;S was revealed in July when chief executive Marc Bolland announced plans to bring in Debenhams chief Belinda Earl as style director to hone its fashion range.
ASOS product director Rob Bready, who is credited with playing a key role in the development of ASOS during his seven years on the board, will leave the company, the group added.
With ASOS having been linked to a move for Ms Bostock for some time, Freddie George, retail analyst at Seymour Pierce stockbrokers, said the appointment was "perhaps the worst kept secret in retailing".
He added: "Kate Bostock adds credibility to the business, and will be responsible for further developing the company's own label ranges but whether she fits in with the unique culture will remain to be seen."