Sussex Police are investigating shocking footage of a man holding a large knife while holding onto the back of a moving bus in Brighton. The video, which has been shared widely on social media, showed the knife-wielding individual smacking the knife against an advertisement three times while shuffling their hands and feet around. The incident plays out in broad daylight with members of public walking past the moving bus. It is unknown when or where exactly the incident occurred. The footage has sparked alarm with Sussex Police working with Brighton and Hove buses to identify the individual. Cl…