It seems that a junior staffer had broken rules and proceedures already in place and that therefore it isn't the fault of the government.
Basic common sense should tell you that you don't send such information via courier and it seems that the staffer certainly wasn't authorised to do so.
Therefore, as awful as this situation is and the costly lessons the government and the civil service need to learn from it, the Tories' ought to get a grip and consider if this would have happened under them! I can't blame them for going gung ho over this (as irritating as their almost naked delight in picking on the government over this issue is), if they want to achieve office it would help them if the government experienced a major crisis that eroded trust with the electorate.
Plus it's hardly comparable with Black Wednesday, esp with regards as to who is to blame, although I agree with Iain Dale about Charlie Wheelan in that this is not just a Westminster issue, it is an issue which is worrying millions of people in this country and is one which concerns and angers us all.