Bill Adderley, the billionaire founder of homeware retailer Dunelm has been unmasked as the biggest private investor in Marks & Spencer.

Mr Adderley has secretly built a near-£250m stake in M&S since the spring of 2012. In that time M&S shares have risen about 40%.

It is understood that he started buying M&S shares last year, but his investment was only revealed on Thursday after his stake crossed the 3pc benchmark.