Our reporter Phil Bayles writes from Russell Square tube station:
If ever there was a need to remind passengers of the need for vigilance against terrorism, this station is probably one of the most appropriate places to do it.
26 people were killed when a bomb exploded between here and King's Cross.
That was just seven years ago but, at the time, the technology did not exist to allow the millions of tube users every day to be screened for bombs and other weapons.
But now the Government believes that science may have advanced to the point where mass screening for not only hard objects but chemicals and liquids too, is feasible. What ministers don't know though, is exactly what this new technology is or who has it.
So, from next month they will begin a hunt for it and are hopeful of coming back with an answer in the Spring.
They already know what passengers do not want: anything that compromises privacy or causes delays.
The answer probably lies in installing the technology at points on underground and mainline stations where passenger movement is already slow; where people have to queue, or at the top and bottom of escalators.
The equipment will probably be portable so that it can be moved around.
Some lessons can be learned from airport security, but the biggest difference there is that passengers turn up at an airport in plenty of time for their flights.
Expecting commuters to allow time for security checks on public transport would not be a popular idea.