The basic business assumption was that if you could replicate a grocery, without actually building a grocery store, in an environment where people had some free time, you could dramatically increase the reach of the company with little capital investment and minimal risk.
What they did was nothing short of brilliant. Tesco did not install expensive flat LED screens, they simply took high-resolution photos of a typical grocery store isle and backlit them. The end result was something that looked very similar to a grocery store experience. Then, they decided to use technology that the consumer already had, a mobile phone (which Tesco would not have to pay for), to act as the checkout device. All Tesco needed to build was the mobile device application that would scan the QR Code (Quick Response) and process the order. While there was a significant amount of expense to build the application and build the delivery distribution system, it was far less than the cost of building stores.
More at Realcomm.