Hello - I have a couple of questions. We have both a layover in Heathrow coming up as well as a starting leg in Heathrow, both BA.
Does Heathrow honor TSA pre-check? If not, why is there a space to add your Known Traveler Number on the BA ticket? (We do not have Global Entry and won't be getting it before our trip)
With layovers in Heathrow, I know that we'll go through customs. Will we then go through security again? Will we collect our checked luggage to re-check through to our final destination?
Lastly - is Heathrow still super strict on liquids? I do stick to the size of course but don't always have it all in a ziplock anymore. Assuming I'll need to do that and pull it out at LHR.

My last layover in Heathrow was in 1999, so I'm a little rusty on how it works there. Thanks!