By Guy Taylor JD Sports reported a dip in full-year pre-tax profit as it flagged a “challenging and volatile” market, after its results were delayed for two days. Profit before tax and adjusting items came in at £917.2m, down 7.5 per cent, which the sports retailer said reflected continued investment in its supply chain and a number of new stores. Sales growth of nine per cent meant revenue in the 12 months to January held steady at £10.5bn, up 2.7 per cent. Investors were left surprised earlier in the week after the ‘kings of trainers’ said it would delay publication of its full-year results …