How early to check in for my flight home from Heathrow?

Three hours would be safer. It can be as much as a 20 minute walk once you are through security to your gate.

Agreed, go with three hours. Heathrow is very spread out and very, very busy. Better to have things go quickly and then kill time than to cut things short and have your flight depart while you are Customer Number 345 in the check-in line. And don't forget to allow time to get to the airport. Coming from London, by any mode of transport, allow at least one hour.

Definitely wiser to go with the 3 hours. My trip last year had me standing in line for security for more than an hour.

Thanks everyone, I will make sure to be at Heathrow 3 hours ahead of my departure time.

Three is my vote. Was there in the fall, and made it slightly quicker, but was lucky!

I do 4 hours. I would rather sit on the "other side" for an hour than stress about being in the security line and check in ends in 20 minutes. On the "other side' there is food, drink, and shopping, so there is something to do.

Claudette, three hours would be good.

The security line is extremely long and slow. But there is some good shopping once you are through. And iy always seems to be a long walk to your gate

I posted this back in August and now I can say from experience and from listening to everyone...3 hours was perfect!! Thanks again.