How much time needed for transfer at Heathrow

Your transfer will all be in Terminal 5 but probably between different satellite terminals (5A, 5B or 5C). 1:45 should be enough for the transfer but even if everything goes to plan I would not count on more than 30min of extra time since once you arrive you may have to take the shuttle train to the main Terminal 5 go through security to go through security and then your out going flight might be at a satellite terminal. This will be 30min at least then boarding for your flight is well underway 45min before departure. That gives you a 30min window assuming no unexpected delays.

I did a similar connection in LHR last week.

DJ

Security at Heathrow can be easy or pretty awful, apparently depending on your timing....they seem to get everyone through fairly efficiently. Our concern: You will see signs (they may have changed in the last few months) that say to remove laptops, etc. Just to be on the safe side, I removed my iPad but left my phone in my purse... sent everything through but my carryons were set aside, along with many other travelers' bags, because our phones were not taken out. The sign specifically mentioned larger electronics. We, along with many others, had fairly tight connections, so lots of anxiety at the table while they sifted through my carry on, backpack and small purse, which took another 20-30 minutes. I think that in previous trips, I must have removed my phone....so my bad, but still... just an FYI.

Well, since England is still officially in the EU and has not exited, you will also need to go thru passport control. Again depending on how the timing this could be fast or not. Check if you can get a fast pass. Security is a bear and you may get pulled out for the random screening. We almost miss our flight, but since our flight from Athens to Heathrow to Chicago was all on one ticket, British air was holding the flight. I think we had little over an hour from out of the plane to on the other. Stress level was very high!

If your flight arrives at a satellite (B or C) and your connection departs from a satellite, even if a different one, do not go back to the main terminal (A). Clear security at the satellite instead.

You won't know in advance - check the departure screen when you arrive if you don't arrive at A.

Do not go through immigration.

when did they change the passport control stop? Curious?

There is no formal 'passport control' ie immigration on international transfers. That isn't to say someone might ask to look at your passport as part of security etc.

If your flight arrives at a satellite (B or C) and your connection departs from a satellite, even if a different one, do not go back to the main terminal (A). Clear security at the satellite instead.

You won't know in advance - check the departure screen when you arrive if you don't arrive at A.

Good advice if your gate is posted but my experience with BA since terminal 5 opened is they never have the departure gate posted until about an hour before the flight so I end up heading to A anyway. So yes, check the departure gates for your connection when you land and if it's posted go through the appropriate security, but if it's not posted don't fret as that is standard operating procedure and head to A.

DJ

As per my opinion, You don't have extra time since the immigration and passport process.

The Seattle flight (at least BA 49) generally departs from T5C, but you can't count on that.

Note that BA has recently increased the critical times for check-in, security, and arrival at the boarding gate:

http://www.britishairways.com/en-gb/information/airport-information/london-heathrow-airport/heathrow-t5

The trip from 5A to 5C can take longer than anticipated if the transit train runs late. On our last flight back to Seattle, we started toward 5C as soon as the gate announcement appeared on my BA app, but the wait for the train was so long we were still standing there when they made a "gate closing" announcement. We were stressed out, but it turned out the announcement was early, as the gate didn't really close until 15:10 as printed on our boarding pass. We sprinted through 5C and arrived at the boarding area all sweaty, only to find a long queue, so we were not actually late But we won't cut it that close again.

Note that in addition to the transit train there are underground passageways connecting the T5 sections. We saw the sign to that as we waited for the train in 5B but it only indicated passageway back to 5A, not to 5C. Turns out there is passage in both directions. There are instructions and photos of the signage on Flyertalk.

We are flying Air Canada next May, Windsor then Toronto to Dublin and returning from Edinburgh via Heathrow. We have 2.75 hours so that should be enough time right? We arrive at Terminal 5 from EDI and depart for Toronto from Terminal 1, according to my paperwork. It sounds like plenty of time but wanted to ask the experts here. Thanks!

Terminal 1 no longer exists. It will be T2 for your Air Canada flight.

ou can use the Heathrow Flight Connection planner to see the steps involved for your particular flight:

http://www.heathrow.com/flight-connections

Basically you follow the purple "flight connection" signs for your desired terminal ( T2). They will lead to a bus which will transport you between terminals " airside" so you do not have to go through passport control. However, this applies only if your luggage is checked through, or you have carry-on only.

If your bags are not checked through, you will have to go to baggage claim to get them, but since you are arriving from EDI you should not have to go through passport control. ( Someone please correct me if I am wrong about that). From baggage claim it is easiest to proceed to the Arrivals hall and take the Heathrow Express for the free transfer to T2. The stop is Central Stationnandnit serves both T2 and T3.

With 2+ hours you should have ample time for that.