ok he was not sticking to strict dvla terminology,
well it is kind of important
but meant the overtaker can't cut you up, so should defer to the overtaken on his left.
He was very unclear if thats what he meant, and as the post was specifically about someone being on the left and wanting to move to the right, and being annoyed that someone already on the right was taking offence if that was indeed what he meant he probably should have got the right and left bit right, and been clear he was talking about cutting someone up. So it could have been dismissed as irrelevant to the point.
albeit reading 168 'recomendation'
LOL ...more plain speaking .. allow for others screw-ups, lack of hp, the hill, or oncoming vehicle
Well some of that is interpretation.
Is it reasonable to try to block someone overtaking?
It seems completely reasonable that once someone has started a maneuver (even if this is somehow a flawed one) to place the emphasis on someone to ensure that its concluded safely if possible, and not to have someone increasing the risk of the situation due to feeling annoyed or something at being overtaken.
The person being overtaken is best placed to deal with this, by following the recomendations, they by default have a gap behind them, and hopefully the person starting the maneuver is doing it safely.
There are plenty of actions open to the Police should someone be overtaking dangerously.
Going back to the OP situation, if the road is a single carriageway (as it appears) and yet two cars are side by side, in seemingly a completely safe manner as the road is wide enough, then surely the maneuver is an overtake by the car on the right?
If that has been commenced in a safe manner (seemingly) then the duty falls on the guy on the left to not move right in a manner that is dangerous. You know, the basic principle, mirror signal maneuver. Plus the specifics on if someone is overtaking you.