The rules require a driver turning at a junction to give way to a pedestrian who is not only already stepping onto the carriageway, but also standing right at its edge waiting for a chance to cross. This is an important safety measure protecting the most vulnerable road users.
KET reference: KET 27: When turning right or left at junctions, the driver must give way to a pedestrian who has stepped into, is stepping into, or is standing right at the edge of their lane waiting for a chance to enter.