Problem: people don't have time to visit Tesco & shop for food. Insight: people hang around the subway a lot as they commute. Solution: Take the store to them by plastering posters of product shelves all over the subway, and have people stroll around "shopping" by selecting the QR codes of their products using their smart phones. At checkout, they can chose to have their selected groceries delivered or pick them up at their Tesco of choice. Clever. So very clever.
Note! This ad won the Grand Prix media lions 2011. Kudos!