I’ve never transited through Heathrow before and I would appreciate any insight as to what to expect. I am arriving on a Friday in September at 11:10 on a Delta ATL-LHR flight. This flight was booked using a Delta Skymiles FF award ticket. I then have an Air France flight to CDG (my final destination) departing at 15:50 (separate ticket purchased from AF, I know the risks associated with delays from the first flight).
I will have no checked baggage on the ATL-LHR flight. I have the older Rick Steves' wheeled bag which meets Delta’s carry-on limits but may be slightly too large to meet the Air France carry-on size limit..
The LHR website “Flight Connections” says (1) the incoming flight and outgoing flight both use Terminal 4 and (2) normal connection time is 60 minutes. I’ve read the step-by-step connection plan, after reading that my questions are: (1) where do I go through immigration? (2) If my carry-on bag needs to be checked for the Air France flight will I be able to check the bag without going through airport security again? Thanks in advance for your help!