With internet grocery sales booming, grocers in the U.K. are competing for warehouse space dedicated to "dark stores." These dark stores are Internet distribution centres, and according to The Guardian, Tesco, Asda and Waitrose are all looking to double their warehouse sizes. Grocery shopping online has grown in the U.K., some 15% of UK grocery sales, worth £900m, were reportedly booked online in the four days from 20-23 December this Christmas. Most supermarkets currently pick most of their Internet orders from their stores, but the opening of more dark stores would result in better availability and faster service. For example, Tesco, the U.K.'s largest online grocer, can fill 4,000 orders a day and offer 30,000 different items–50% more than the average store from its dark store in south east London, said a report. To read full story, go here.