Boris (and everyone else who promotes the idea of detectors) seems to be ignoring the fact that whilst creating a target with the size of queues they will undoubtedly cause, the scanners will only deter the most incompetent terrorists.
Why? Because the LU is a huge, open system. You can simply climb a small fence and from there get to any other part of the system. Securing the stations alone will not make a difference, and will almost certainly lead to a false sense of security which could put travelers in a worse situation than before as their guard will be lowered.
You could solve this by securing the entire of the underground system; closing it off, but that is going to cost an astronomic amount of money and will only be as reliable as the least secure part of the whole system. Or you could spend the money on gathering better intelligence, more policing and maybe starting to solve some of the fundamental problems that drive people to terrorism.
People who advocate detectors at LU stations either don’t understand the security situation, or are only interested in the “fell good” response the suggestion would have with the public.
There are a couple of good quotes from Geoff Dunmore, operational security manager (March 2006) for LU:
“…the network would not be the right environment for the technology.”
“Basically, what we know is that it’s not practical”
“Finally there’s also the risk that you actually create another target with people queuing up and congregating at the screening points.”