This (see diagram in next message, can't put it in this one?)
Quiet country road, NSL but very twisty and turny in a rural area near Bristol.
I'm driving along at about 30mph behind a small lorry towing a trailer with small tractor on, then a car in front of him and a large, wide tractor in front of him. BMW comes up behind me and starts flashing his lights and driving too close. I slow down. We get to a roundabout and the BMW driver pulls out to the right, put his/her foot down and overtakes the queue on the right and then pulls in in front of the tractor, cue mass braking to avoid a pile up.
2 miles down the road I get to the red traffic lights with a queue of about 15 cars. Guess who is in front of me 
Probably the most dangerous driving I've seen.