Airside would be quicker by a good 15 minutes. If going landside the tube is better since it's right by T2 whereas HEX is a bit of a hike. The T2 Flight Connection centre is quicker than the T5 equivalent too, and as with T5 there are biometrics involved after the UK + Ireland passport check. You don't even need a boarding pass, you can collect that from T2 if necessary.
Originally Posted by
LondonElite
If you are late to board your next flight (ie because your Madrid inbound was 30 minutes late - not unusual at LHR), you may find yourself having to buy a new ticket to BHD.
That's certainly a risk worth highlighting however on a 1 hour 40 minute connection then you are probably safe with a delay up to 45 minutes. It takes about 30 minutes to get from T5 to T2 airside all told, it's quicker than getting through T3. EI starts boarding earlier than BA, and will leave 15 minutes early if they can, whereas BA won't leave more than 10 minutes early.