Moderator: American AAdvantage, Signatures
Join Date: Jan 2008
Location: London, England
Programs: UA 1K, Hilton Diamond, IHG Diamond Ambassador, National Exec, AA EXP Emeritus
Posts: 9,765
Check-in must occur no sooner than 45 minutes before departure at LHR, though conformance is also in place which means you cannot enter security with less than 35 minutes of time to make your flight.
My point above was that any issue/delay could impinge on connection time; definitely the more one can do before getting to the airport the better, though I stand by my post that 4:25 is tons of time at LHR, and planning for a multi-hour delay is just wasting time. BA will get you there eventually, and if there's a delay it's best to be flexible and roll with the bumps.