Caught the silencer on the shut plate in the road between a set of gates causing it to blow. I could see the silencer was well buckled on the front rim so I took the system off for a better look. There was no hole luckily but the collision had caused the flange where the pipe joins the cast iron manifold to become deformed. With the help of 'er indoors holding the system up I placed the flange down on top of the ball of a towhitch and tapped round with a small hammer till it was back in shape.
Re-fitted - good as new - almost!