I once had a Cessna 152 almost collide with me. It was passing above me from right to left and I decided to turn gently to go behind it and give plenty of clearance. Then, it suddenly commenced a diving turn towards me, I turned to keep it in sight and had a hairy few seconds trying to decide what it was doing before managing to break away. It looked as if it was trying to formate on me, he was that close.
I recognised the aircraft from its colour scheme, and went to the airfield it operates from to find out who had been flying it.
An instructor owned up to doing steep turns (with no clearing turns to establish a look out) and neither student nor instructor had seen me until I broke upwards and away from them. His excuse was that it was the end of the day, he was tired and not expecting anyone to be there.
It was a classic case of high wing-low wing obscuring the other aircraft. If I had seen him doing clearing turns it would have alerted me to his possible intentions, and he might have seen me.
Ultimately no harm done, but I was glad I was wearing a parachute. I learnt about flying from that, not sure he did though.
RD