It was a mob scene for Brad Pitt in London last night, where he and writer-director Guy Ritchie — yes, the father of Madonna’s newborn Rocco Ritchie, who was reportedly with his mom in Los Angeles — showed up for the premiere of their new movie, “Snatch.” Pitt, who plays an Irish character named One Punch Mickey (sounds like shades of “Fight Club”), in the British-made gangster thriller, caused screams among the 4,000 bystanders outside the West End movie theater when he showed up in a limo with Ritchie. Then the fans surged forward, and police had to ask Pitt to stand back or else face being squashed by them. “There were kids getting crushed at the front,” Chief Inspector John Moore told the Associated Press. “I told Mr. Pitt that ‘You owe it to them not to put them in danger.’ ” Pitt obliged, and ceased signing autographs. He also stopped talking to reporters, though he did manage to say that he did the movie because he “liked the story” before handlers hastily ushered him away.