As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LHR - CREW REPORTED LEADING EDGE SLAT ASYMMETRY EICAS MESSAGE DURING CLIMBOUT. EMERGENCY DECLARED FLIGHT RETURNED LHR LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPAIRED PROXIMITY SENSOR S279 THAT HAD BROKEN WIRE. SYSTEM GROUND CHECK NORMAL OPERATION.