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. **ORIGINAL REPORT WAS AALA202311223023: MAINTENANCE FOUND A RUNNING LEAK COMING FROM THE LEFT-HAND MAIN LANDING GEAR SIDE BRACE FORWARD SWIVEL FITTING AND PIPE ASSEMBLY (AALA202312197121), REPLACED THE SWIVEL FITTING AND PIPE ASSEMBLY PER AMM 32-32-04. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED.