It's as simple as this.
The car driver had two choices.
Drive into the side of the truck and cause an accident or brake and wait for the truck to pass.
He chose the first option, caused the accident so therefore he is to blame. END OF THREAD
True, but equally the HGV driver is a professional and in charge or a lethal machine (Most Malcolm group HGV's are six axle artics) he should drive defensively and use anticipation.
He should have realised the car driver was running out of room, he could have just lifted off and let him out given the relative low speeds involved, perhaps he could have moved into lane #2 although he may have had a lane restriction preventing this or perhaps another vehicle along side him.
As professional drivers, we (I am a Class 1 HGV driver by trade) have to allow for Joe public most of whom have no clue how to drive, never mind around large heavy vehicles, given the size & weight difference, that truck could easily have "hooked" the car & ran over it with disastrous concequences.
Yes, the car driver was a grade one Turnip who certainly didn't check over his shoulder prior to pulling out but equally the truck driver could & should have anticipated it happening.
Tbh, this sort if thing happens daily in my line of work, thankfully, I've not (yet!) been involved in such an accident by doing what IMO the trucker didn't.
No, he's not to blame as far as insurance companies are concerned, nor it would seem by his employers, that said, he still IMO fell below the standard you need to drive one of those things safely.
Assuming, of course, we have all the facts and the perspective of the HGV driver and view in his mirrors, which , alas, we don't.....