Some great info here, thanks guys.
I was looking at a pic of the Harrier (II, I think) with the gear extended and I note the nose gear doors are closed at the tyre end of the system but the leg end is obviously open around the pivot end of the leg with a very tight opening allowed around the leg. Why is this? Does the door-closed system prevent damage to internal systems (eg Hydraulics) during the vertical take off or landing, from FOD produced by the downward thrust or is there something more to it?