As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 731, LGW-PHL: DURING CRUISE, GREEN HYDRAULIC SYSTEM QUANTITY BEGAN DROPPING. CAPTAIN DECLARED EMERGENCY INBOUND TO PHL. FLIGHT LANDED WITH NO DIFFICULTIES. MAINTENANCE REPLACED AN O-RING ON THE GREEN SYSTEM HIGH PRESSURE FILTER MODULE.