I was driving along the M3 yesterday near Fleet and a veyr large brown paper bag hit the front of the car (when I say large I mean duble thick sack size). Within seconds smoke was flowing from the back of the car. My mate looked in the wing mirror and saw bits of paper, quite big, floating back from the car on fire. The smoke was getting worse so we pulled over onto hard shoulder. Looked underneath and the bag was caught in the downpipes flaming nicely. Managed to poke it out with a stick from the side of the road. I'm a bit concerned that nearby pipework could have been damaged. The smell of burning was terrible.