25.—(1) Every pedestrian, if he is on the carriageway within the limits of a Zebra crossing, which is not for the time being controlled by a constable in uniform or traffic warden, before any part of a vehicle has entered those limits, shall have precedence within those limits over that vehicle and the driver of the vehicle shall accord such precedence to any such pedestrian.
A bicycle is a vehicle for the purpose of this legislation (as referenced somewhere else, but bollocks if I'm looking for it).
"Give way" being operative here.
The Zebra, Pelican and Puffin Pedestrian Crossings Regulations and General Directions 1997