Hello FTers! Though this is my first post, I've been browsing FT for a while now. I'm hoping your collective intelligence can help me plan for an upcoming trip.

This summer, I'm flying from IAH to LHR on UA4, which arrives in London at 9:40. My impression is that the flight might arrive on the tail end of a crush of morning TATLs. Around that time of day, how much time should I anticipate requiring to clear border control and customs at LHR T4?

All estimates are welcomed, as it would help me to know both an average time and what kind of +/- spread to expect.

And FYI, I ask only because I have to make a train reservation for a meeting just after lunch that's more than 2h from LHR and want to know if I need to rebook on an earlier flight.