A punter’s use of one of the oldest tricks in the book has captivated a very modern audience – with millions on social media watching his moves. The viral footage, taken by a passenger, shows the man nonchalantly lying back and using his feet to push his riverboat down so it comfortably travels under a low bridge in Canterbury. His fancy footwork is then applauded by those on board the ‘Black Pearl’ as the 22-second video ends. The Canterbury Historic River Tours worker was doing something known as legging, a centuries-old technique of passing through narrow waterways when unable to use other …