Let's face it, admin crap aside, there's a culture of secrecy pervading all three services which carries things to the ridiculous level. Most "classified" material is either available on the internet or in specialist mags given enough time, perserverance and computer time, or really doesn't matter all that much in the first place.
A former Flag Officer Submarines once told me that the only truly secret issues for the RN were missile targeting data, sub patrol box locations and the design of the unique, onboard reactors. The rest, he said wearily, was little more than bureacratic nonsense in place to make inadequate people feel important.
Whitehall will do what it does best when faced with having to put up a smokescreen against embarrassing public access to records. It will classify entire rainforests'-worth of bumf - needlessly - and stall, prevaricate and obstruct legitimate inquiries.