Push comes to shove a road user is entitled to the whole of the lane they are in. No one is going to expect an 'overtake' from the left of them, particulary if they are an older slower nervous driver (that car alone should be enough to say 'ditherer') or a youngsters on the phone texting whilst whizzing from MacDonalds to McDonalds (not stereotypes, just examples people) Think you'd be on a bit of a sticky wicket legally trying to apportion blame him if he had hit you.
Think we saw you coming out of Salisbury on the Devizes Road on saturday, black street triple with helmet mounted camera? wouldn't have seen us as we were in a diesel MG