Help"d out a flip flop who was loading waste oil in an ISO tank,said to me he wasn’t sure what to do.Told him he would have to load 30.500 litres,and got on top and showed him the dip chart.Then I said open the lid, fxx me it was still under pressure from the previous tip…I explained what the outcome would be if he opened a man lid that was under pressure.What sort of ■■■■■■■■ boss would allow a man to put himself into that situation.Obviously he’d had none or minimal training.Boss"s like that have no conscious.Just the pursuit of profit.They are a cancer in our industry
Unless the boss himself assessed the driver Rog I can’t see what more other than check that he had the relevant qualifications he could have done. By the time the driver had opened the first of maybe the second lid clamp I’m sure he would have realised that what he was attempting to do was A BAD THING and maybe vented it first. Or maybe not, in which case a video phone is your friend! 
No scruples?
I had a boss once that didn’t even have monopoly. Hated that man.
Used to load out of a chemical plant and on the wall was exact same scenario on a safety poster.
Blokey undid the manlid and it blew him clean off the trailer for quite some distance, his body describing an arc towards the ground, life expiring as it did so. 
You possibly saved his life, and you can do a RIDDOR
No scruples?
Bet he sang soprano.