Somebody on a recent thread stated that in his/her view, see and avoid was a load of hogwash, and that collisions were primarily avoided by the statistical unlikelyhood of flight paths converging.
In 200 odd hours I can recall the need to avoid five times; three were very close and to be honest one was so close and quick that we flashed past each other before either got a chance to react and that was over WCO, an early lesson in not flying over landmarks or beacons!
After seeing Farnborough's radar screen, I'm much resigned to the fact that I simply have not seen at least half the traffic that was probably visible to me, and I reckon I'm pretty diligent when it comes to lookout.