Passengers flying through Heathrow Airport, Terminal 5, will be photographed and fingerprinted twice before being permitted to board domestic flights. The British Airport Authority, which runs the new terminal through which all British Airways passengers will travel say this measure is "necessary to prevent criminals, terrorists and illegal immigrants trying to bypass border controls."
The only reason why this may be necessary is that the design of the new terminal permits international and domestic passengers to mingle in the secure area. Theoretically, transiting international passengers would be able to swap boarding passes with a domestic passenger circumventing border controls. On balance, it just makes sense to ramp up the big brother factor if it means the BAA doesn't have to follow the non-intrusive but universal designs used by every other airport I have ever been through.
The BAA also says the fingerprints will be discarded after 24 hours, unless -- of course -- they are of interest to the police. See: Heathrow airport first to fingerprint - Telegraph. Via the ever vigilant Boing Boing: Heathrow Terminal 5 to fingerprint domestic passengers - Boing Boing.