Further to & explaining the Highway Code stuff that ksand24 posted about zebra crossings...
Yes, the way my driving instructor explained it (for a driver) is that you need to slow down & be prepared to stop. Technically (according to what he said), the driver isn't
required to stop until the pedestrian puts a foot (a step) into the crossing, upon which the driver
must stop. Obviously, if you haven't slowed down anyway, you might have a hard time stopping by that point.
Knowing this helped me as a pedestrian. You want to make it clear that you are crossing - look at the driver (I call that 'giving them the look' or 'the stare') and start to step into the crossing. Unfortunately, with some drivers around, if you are staying completely out of the crossing & keep waiting for them to stop before you start a crossing attempt - they'll probably just keep going. You needn't throw yourself in front of a car or anything, but just get a foot or a toe out there, and show that you intend to do this now - you mean business on getting into that crosswalk!

If they don't stop once you are in the crossing (even a foot or a toe), the driver is breaking the law.
Crossing with an island in the middle, each half is a separate crossing.
HTH!
