It is a skill treasured by drinkers and passed down the generations, requiring pinpoint planning, nimble footwork, subtle eye contact and the occasional well-timed shove. But traditional tactics for getting served first in the crush at the bar could be consigned to history if a London pub?s trial of facial recognition scanners is a success. The software, more commonly used by police and airport security, has been deployed at a cocktail bar in the City to ensure customers are first-come-first-served.