As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LHR INFLIGHT T156/24AUG - LEFT AND RIGHT NUMBER TWO LAVATORY SMOKE ALARMS WENT OFF AT TAKEOFF FOR ABOUT ONE SECOND. NO EVIDENCE OF SMOKE. RESEATED ELECTRICAL CONNECTORS FOR SMOKE ALARMS IN LEFT AND RIGHT NUMBER TWO LAVATORIES. SYSTEM GROUND CHECKED NORMAL OPERATION.