UPDATE 21:48UTC Pilots were wearing oxygen masks while declaring mayday.
UPDATE We have confirmation British Airways BA327 safely landed at LHR.
UPDATE 23:35UTC We receiving reports British Airways BA327 has technical issue.
UPDATE 21:34UTC British Airways BA327 is on final approach runway 27L.
UPDATE Captain Mitch Neve explains AirLive.net different cases of emergency:
BREAKING British Airways #BA327 from Paris CDG to London LHR is declaring an emergency. Live: http://t.co/bODtk7G1VQ pic.twitter.com/GqbakJWEjt— AirLive.net (@airlivenet) July 27, 2015