Such problems are made easier and more likely because there is no routine security at any of our railway stations. Years ago you could not access the station platform until you had bought a ticket. Presumably these characters can ride the railway network all day for free.
Absolutley - staffing stations properly would be the single biggest deterrent to these little *****. But of course, extra staff requires more money, so it's not gonna happen.
Instead we get the cheap option of CCTV cameras which we're told provides 'security' and 'safety' (a big comfort when someone's threatening you with a knife of course, as you think "oh well, at least this is being captured on camera."). Of course, let's overlook the fact that they've had CCTV images of this gang since November but still don't seem to have made a single arrest...