Assuming the USA has the most stringent screening in the world is just not true. They are average.
However the UK Department for Transport chooses not to allow any UK airport to allow unscreened passengers from anywhere else. This is unlike most of the rest of the countries in the EU which choose to allow unscreened passengers who have been screened in another country deemed to have sufficiently good screening (EU, Schengen airport, or USA).
With the current xenophobic tendency in UK government and general noisy chaos in UK politics, this is not going to change any time soon (years). All that can happen is that it is made more efficient, which may happen, if Heathrow Airport ever manage their staff properly and get to build larger facilities.
Originally Posted by
Raffles
The 'hub' issue is actually the biggest problem at Heathrow. Huge number of people passing through, contributing nothing (you don't even pay APD) and clogging up the system.
They pay the high Heathrow Passenger Service Charge.