So just bought a camelbak with the intention of having it empty, going into the arena area and filling it. Easy to carry, holds 2L, saves going for refills etc etc. Only to then be told by a friend that I wouldn't be aloud to take it in. To me, that sounds utterly bonkers, not being allowed to take in, what is essentially a rucksack with a empty plastic bag inside. Can anyone confirm this is in fact banned? And in that case offer some rationale as to why on earth I can't have a rucksack with a plastic bag inside? Thanks.