I was thinking about exactly this. I go to Lords every year with my dad, there are bag searches and body searches (mostly for alcohol mind). There are a few points outside of the ground where someone could set off a bomb and kill 25+ people easily. Have we reached the point where you would want to set up a perimeter around any event and allow no bags within say, 1 mile, of the venue? Is this practical?
No bags at the event wouldn't have saved anyone last Monday, the guy wasn't in the arena.