Good awareness from all involved, I would also have slowed and allowed them to turn.

But the fact remains that although it is very reasonable for this lorry to move to that lane to then turn given its length, once it has done so, it then needs to cross an active lane of traffic to make the turn. The Highway Code clearly says if you are doing this you MUST give way to traffic already in the lane you are crossing before making the turn. Something the lorry not only failed to do, but clearly made absolutely no attempt to do.

These rules exist for a reason, and that particular one is not a mere suggestion.

A less experienced cyclist might not have understood what was happening and could’ve ended up under that truck.

Maybe the driver noticed the cyclist slow and give way, but the fact remains that they did not even attempt to give way to that cyclist, and although the cyclist did the right thing to slow down for their own safety, they are not required to do so, and if the truck driver had followed the rules of the road they wouldn’t have needed to.