My husband and I had a 2-hour layover in LHR last year that, thanks to their %$#@!! "Security" nearly wasn't enough. We arrived gasping at the gate about 5 minutes before our flight back to the US and were told that if we'd been more than 10 minutes late they would have offloaded our bags- but it appears we did have a little leeway left because we'd checked bags.

And, on a domestic flight last year, I tried to get on an earlier-than-scheduled connection and, even with 1/2 hour to spare- because they said it wasn't enough time to transfer my checked bag. So there must be some sort of bag-matching there, too.