US investor Harris Associates has increased its stake in JJB Sports to 17.9 per cent, making it the biggest shareholder in the recovering sportswear retailer. Harris upped its stake to 116m shares from 104m over the last few days. Last week it raised its stake from 93m. The share-buying spree takes Harris Associates ahead of Crystal Amber, which has a 15.4 per cent stake in JJB. Chief investment officer at Harris Associates, David Herro, has been a long-term shareholder in the retail chain.