The quaint licensing laws of the United Kingdom used to contain the notion of the "bona fide traveller". At certain times and places (Sundays? Scotland and Wales?) inns were not permitted to serve alcohol to local customers, but could only serve genuine tourists, people who travelled "in good faith".
In some parts of the country, people would go on Sunday coach trips to the next town, where they could drink as travellers. This was certainly against the spirit and letter of the law - they were travelling in order to drink, not travelling "in good faith" - but they usually got away with it.
I remember hearing the great war correspondent James Cameron tell a stirring tale of having battled his way back to Scotland across several continents, perhaps from some remote corner of the Korean or Vietnam War, only to be denied a drink in the pub nearest his home because as a local he didn't count as a "bona fide traveller".
Today, in the photogenic but dysfunctional Terminal Five building at Heathrow Airport, the airport authority hoped to verify travellers' bona fides by taking fingerprints. Are you permitted to buy cheap gin? Are you permitted to get on this charabanc to Rhyl, with or without baggage?
Biometrics and identity cards can maybe tell the authorities who you are and where you live, but they are not enough to reveal your intentions, your bona fides. Did you pack this bag yourself? Has a mysterious stranger given you anything to carry? Are you conspiring to overthrow, put down, or to destroy any government by force? (tick YES or NO)
BAA claims that fingerprints are required to prevent terrorists from stealing into the UK, but of course what they really mean is "known" terrorists - people whose names and fingerprints are already on the blacklist, or people who are already "wanted" in other countries. Maybe we need some more technology - perhaps lie detectors, or the "tunnel of truth".
Meanwhile, there are suspicions in some quarters that the physical layout and passenger processing are principally designed not to promote the security of the country and its transport operations, but to promote the commercial profitability of the airport and its retail operations. Fingerprints overruled by the Information Commissioner, they are going to take photographs instead. Oh well, so that's all right then. Rhyl, here I come.
See also: Heathrow Terminal Five, Actually You Can't Fly Either