Defensive driving?..Once over you very rarely had to do that amongst other trucks, it was mainly reserved for car drivers, because you were once fairly confident that you were not going to be ■■■■ ed up or left hanging by your average fellow pro driver, …
As for today, since say last 10 to 12 yrs?..different story.
I’m always aware nowadays that I could possibly need to go in defensive mode when approached by a truck. 
Ok, not in an ‘‘obsessive neurotic can’t relax’’ sense, but it’s always in the back of my mind…‘This approaching truck could be manned by one of those ‘Car driver with Class 1 licences’’ knobheas/ wastes of space. 
If I’m being overtaken for instance, my first check is (sorry chaps got to say it 
)
Is he wearing his hi viz? .not saying you’re all like that, but most of the time I ain’t regretting being careful.
Or at the other end of the crap driver spectrum…
Is it some overblinged monument to bad taste being driven by a nutter.
Either way I’m expecting a near hand overtake with a trailer shaving my windscreen.
(You rarely ever got that once over, we had a flashing in system that worked, then the knobs thought they were above it, and the simple system that worked, was ■■■■ ed up by em, so many times nowadays with some of them it’s guess work or blatant ‘I’m coming in, deal with it’’ attitude. )
It’s got to the stage in all scenarios, not just being overtaken, but r/abouts, junctions, and everything else…I just assume incompetent and/or nut job, and if he turns out to be a proper pro driver it’s a bonus.
So far at a guess it’s 70% driver.
30% …not as long as he has that proverbial hole.