Diners at a branch of Yo! Sushi in Soho, central London, see their burgers delivered on a flying tray. The stunt to promote Japanese rice-burgers allowed the food to float past tables without a waiter. The 'I-tray' gadget is made from a lightweight carbon fibre and has four propellers. Two built-in HD cameras allow kitchen staff to deliver the food via a real-time video broadcast viewable on an iPad screen