I know that bit of road quite welll, I fail to see why the trucker needed to use lane 3 - you can turn right from lane 2 iirc.
The trucker was in the wrong, the Copper more so imo.
He did not see any reason to have his Blues & Two's on! Despite travelling
@130 odd mph, nor did he appreciate that the truck probably wanted to turn right.
Sure the trucker should have stayed in lane 2 - he should not have used lane 3 at all, and the trucker knows that (or, he should!)
The Copper also did not use his horn, despite opportunity to do so imo.
The trucker should have used more caution as on a left hand bend his off side view is severely restricted - again, the smart arse Copper should have known this.
Seems to me that the Copper was going too fast, thinking too slow and had he been thinking quicker, he would have gone up the inside of the trucker, given that the trucker was already turning right coming towards a roundabout with a right exit!
Both wrong, but one has the upper hand over the other!