Martin Compston was a footballer with Greenock FC when Ken Loach cast him in ‘Sweet Sixteen’. And of all Loach’s recent finds, it’s Compston who has carved out the strongest acting career. So it’s a shame to see him lowering the tone with ‘Piggy’, a dime-a-dozen, not entirely terrible London thriller. He plays Joe, whose brother gets murdered on his way home after a night out. What looks like an open-and-shut case (the entire pub watched some local wrong ’uns have a pop at the victim) stumps the police. Then a man called Piggy (Paul Anderson) shows up, claiming to be a mate of Joe’s bruv. Piggy is here to wreak some nasty revenge, but Anderson’s grandiose over-acting is a dead giveaway that he might be a figment of Joe’s imagination.