Originally Posted by
stifle
The UK does not distinguish between passengers' destinations when deciding what type of security check they will receive at the main checkpoint. Those travelling to the USA may be subject to additional checks such as pat-downs and shoe carnivals at the boarding gate.
Indeed. If there are any exceptions to that, they would be very, very rare.
During some given hour at some screening checkpoints, it may not take too many opt-out-of-strip-search-machine-screening passengers' screenings before things get backed up rather extensively for some passengers.