sorry I was away working at reading festival.
I would agree it's not legislated per se, however without due care and attention maybe a high bar to convict, the charge of driving without reasonable consideration would be one that should cover it.
It does cover miss use of any lane or
unnecessarily slow driving or braking without good cause. whilst not an actual offence it would in some situations be covered. obviously only my opinion.
I suspect the attitude rest would have s big part.
in Scotland there are many road signs about not impeding following traffic.