Well said Brianh.
The closest 'near hits' I have had were both in C under control. A little Cessna 152 (on approach) was joining the circuit but had got too close.
Tower (I was on Tower) hadn't seen him due sun. I spotted him and turned left (which I suppose is the worng way, but instinct kicked in and we were converging for a hit on my right) with about 100m to spare, (s)he never saw me (I asked later).
Tower "FXR why did you turn?"
Me "I don't like loud noises"
No blame really, I suppose approach weren't watching my blip??? With the new TCAS thingy this probably won't happen again.
The other was a similar incident many years ago, this time me in a 152 and a bl@@dy huge C130 popped around Cape Palleranda surprising both me and the tower. They thought he was further out ... why ... dunoo .. too low for the Palleranda RADAR perhaps????
AK