A volunteer passes through the new body scanner installed at Paddington Station in London for a four-week trial. Photograph: Chris Young/PA
The passenger scanning trial at Paddington train station is one answer to a very difficult question: what to do to protect public transport against suicide bombers and other terrorists. Passengers on the Heathrow Express, the fast train from central London to the capital's principal airport, are to be picked out at random and sent through a full-body scanner that will reveal any explosives on their person.
Comments on Spy Blog, a self-declared examination of trends towards "more widespread surveillance", scathe the trial for being little more than an exercise in confirming what we already know - that "the technology is still orders of magnitude too slow and too expensive, even for limited use on the Heathrow Express".
They also make the point that the Heathrow Express - which at £13.50 costs more per mile than most aeroplanes - is not typical of the wider public transport network. Its aiport-bound passengers are prepared for security checks ahead, and the train is not packed out during rush hour with people trying to get to and from work. If the trial works at Paddington, that does not mean it will work on busier intercity trains or commuter and underground services. Indeed, it is hard to imagine how it could.
Just because one train is safe from explosives that does not mean others are. Before the Madrid train attacks in March 2004, some luggage screening was in use on Spanish long-distance services but such measures can never protect an entire network.
