After 15 years in the role, ASOS boss Nick Robertson is standing down as Chief Exec – with immediate effect and no plausible explanation.

Robertson, who founded the fashion pureplay in 2000, will remain on the board as a non-executive director. He is succeeded by Nick Beighton, who has been preparing for this day since he joined ASOS in April 2009 as CFO. Beighton has worked closely with Robertson on the growth of the company and in October last year, was appointed Chief Operating Officer, widening his management responsibilities beyond finance. He qualified at KPMG as a chartered accountant and is a former Finance Director of Matalan.

The reshuffle was widely expected as was Beighton‘s promotion.

What started as a British site offering cheaper alternatives to celebrity outfits, has since transformed into a global fashion powerhouse worth £6bn, allowing Robertson to cash in £20m earlier this year when he sold shares in the e-tailer. His remaining stake is valued at around £210m.

It is understood that the decision was Robertson‘s, who felt it was time to move on following a turbulent 18 months which saw a warehouse fire and a string of profit warnings. A source close to the business told The Guardian that Robertson “should be applauded” for taking a step back from the empire he created, because so many entrepreneurs try to hang on as leaders despite lacking the skills needed to keep up with running the company. The source said: “It suits him and the business to move on.”

In a statement from Asos, Chairman Brian McBride said:

“On behalf of everyone who works at ASOS, I‘d like to acknowledge Nick Robertson‘s extraordinary achievement. His passion and vision have built a start-up into a world class company. We are all delighted that Nick will continue to contribute to the company he started.

We are fortunate to have such an able successor for the CEO role in Nick Beighton. Nick has unique experience of the company built over six years, equipping him to drive ASOS along its growth trajectory to become the world‘s leading online fashion retailer for 20-somethings”.

The filing does not include a statement from Robertson himself.