The Arena bombing happened outside the actual arena in a publically accessable area. Nothing to do anyone taking stuff past security, through the turnstyles and into the arena itself.
So a terrorist could turn up on Hardcastle Street outside the Cheadle End and nothing could be done unless youre going to corden off the surrounding housing estate, and even then it would shift the attack further afield and still happen. Also, why single out sports stadium and events arena? Are we also going to have bag searches, or even bans, on trains and buses? In shopping precincts? At christmas light switch ons?
9B Stockport Edgeley, 9F Heaton Mersey