Bella was having a meal at a restaurant when she suddenly felt unwell. In her panic to find a bathroom, Bella went upstairs beyond a sign, placed there by William, the owner of the restaurant. The sign read 'Private. Not for public use'. Bella found a bathroom at the top of the stairs. Bella felt faint as she was coming out of the bathroom and fell down the stairs that were uneven. Bella sustained a head injury. Paul, a waiter at the restaurant, was annoyed at Bella for ignoring the sign. Paul shouted and raised his hand as if to hit her, but he was restrained by some of the restaurant's customers. Discuss William's legal liability, if any, for Bella falling down the stairs.