I have just read that the US is considering extending preclearance to Heathrow & Manchester.
US Considers Expanding Airport Preclearance
My question is how will it work at LHR. Presumably you would require dedicated gates & concourses. Fine if you dedicate a concourse of T5 & a wing of T4, etc, but very hard in practise without building new infrastructure as there are not many spare gates. Could you build an additional US preclearance story above the existing concourse? It could be incorporated into the "toast rack" in the long term but what of the medium term? Any thoughts as to the feasibility anyone?