Clear ahead at the zone
The situation
Noor reaches the zone clear ahead of the boat chasing her. The chaser dives inside at the very last second, shouting for room.
The question
Does the boat that was clear ahead at the zone owe the diving boat room?
The ruling
No. When a boat is clear ahead as she reaches the zone, the boat that hasn't reached the zone — the one clear astern — must give her mark-room (rule 18.2(a)(2)), not the other way around. The chaser can't manufacture an inside overlap inside the zone and demand room; Noor is entitled to round, and the chaser keeps clear and rounds behind. (Had they been overlapped at the zone, the inside boat would get the room — but clear-ahead at the zone wins.)
Clear ahead at the zone gets mark-room from the boat behind — a late dive inside doesn't steal it (rule 18.2(a)(2)).
Opens the situation on the boat-length grid — scrub it and see exactly how the boats meet. Free, no account needed.
Rules cited
See the underlying rule: Rule 18.2 — Windward Mark — Clear Ahead at the Zone.