It is stated in the traffic rules that 'at pedestrian crossings where traffic is not controlled by the police or by traffic lights, drivers shall give way to pedestrians who are already on the pedestrian crossing or who are about to enter it.'

When you have an obligation to give way you must also drive in such a manner that the pedestrians understands that you are going to uphold your duty, e.g. by adjusting your speed. You therefore always need to check if there are any pedestrians crossing or about to cross the road at the crossing.