I am flying to JFK-LHR-AMS on BA next weekend, with an airside layover ov about 2 hours. I will have my PCR text result in my hand (can also use Verufly for the flight to LHR) and since I have been boosted and have my CDC card with proof I do not have to quarantine in The Netherlands as of now.
My question is that on the return section AMS-LHR-JFK, I have about 5 hour layover at LHR. I will have my Antigen test done the day before departure in Amsterdam along with the US self-declaration form (which no one looks at!) and will be issued with both BP's for the AMS-LHR and LHR-JFK sectors. I was wondering if I could go landside during my layover to meet with a friend for lunch, plan is he will pick me up and we will go somewhere near by for a leisurely lunch at a restaurant and catch up after a few years etc. Since I will already have my LHR-JFK BP in my hand, when I return back to T5, will I have any issues going through security to get back airside so that I can continue my flight? Reason I am asking is if I get stopped by some BA staff who say for example the Antigen/PCT test is no longer valid since I entered the UK even it was just for 3-4 hours. I imagine since I have my BP I will be able to just go right through security but just wanted to check if anyone has any insight. Also, when I arrive at LHR and go through the immigration, are the Egates in use now? As a US citizen I assume I can use them, and also, would I have to present any testing documents etc. at immigration to be let into the UK and go landslide?