Someone commented that space might be needed to replace the ticket machines. If you magnify the new pic you can see the machines aren't all that huge unless they're very deep into the wall at the back. Think of the cash machines in your local building society. They're not huge.
The problem is that if you want to run over a significant number of people in one go you'd just drive at the bus queue on the opposite side of Guildford Park Road which is often quite long with people travelling up to the hospital. I do remember the attack on Glasgow Airport in 2010. It was pretty horrific in its planning and execution. Maybe Network Rail has been advised of a specific threat, but as someone said the gap is large enough to drive a truck through, so what's the point of what's been done?
I must say that when I walk acros Waterloo Bridge I feel reassured by the lumps of concrete keeping vehicles safely off the pavement!
