As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT DIVERTED TO LHR, AFTER TAKE OFF PRIOR TO EXTENDING FLAPS THE CENTER HYDRAULIC SYSTEM QUANITY DROPPED TO ZERO. AIRCRAFT LANDED SAFELY AT LHR WITHOUT FURTHER INCIDENT. (OPEN)