Greatest Public Interest - Who Decides?

Chris Paton picked up an interesting Grauniad article in his blog yesterday. This notes that a number of historians are considering taking the FCO to court to force them, under the Public Records Act, to release into the public domain thousands of files dating back to the 1840s still held by the department. What caught my eye was the promise from the Government that the records "of the greatest public interest" will be handed over to the National Archives over the next six years. That rather begs the question of who decides what is "of the greatest public interest". Given that one collection is entitled "Birth, death and marriage resisters" one wonders whether genealogy studies feature in the criteria.