The obstacles are numerous, and they can take the form of either political or physical obstacles, as it were. In terms of the political obstacles, persuading people within the bureaucracy who have secretive habits to operate in a more open way is the biggest. This is where the importance of leadership comes in, which is something John explained extremely well. You need someone with a strategic kind of viewpoint on this and also to forcefully say this is what you must do.
Of course, reversing habits is also difficult with regard to getting the mechanisms working again. If there's a great deal of delay, for example, in the system, and people are in the habit of letting freedom of information requests sit in their in-trays, it requires a kind of burst of energy to make the mechanisms work more quickly. It also relates to things like the appeal system and other parts of it, which all need to be made to work quicker.
The answer, of course, is the classic answer to everything in government, which is that it probably needs more resources as well.