The impression is sometimes given that we are on a one-way drive towards greater openness in public life, as more and more state information is constantly being revealed.
But in fact change is not always in the same direction. Public bodies sometimes cut back transparency, deciding to keep secret material which previously they might have disclosed. One example of this is the Metropolitan Police Special Branch, the section of the force whose duties have featured monitoring political subversion and which is now part of the Met's Counter Terrorism Command.
A recent decision by the Information Commissioner makes it clear that the Metropolitan Police is now highly resistant to releasing Special Branch (SB) records under FOI, even when they are no longer current, and that the Commissioner is likely to support such a refusal.
The Police argued that SB documents have generally related to security bodies and so are absolutely exempt from freedom of information requests. The Commissioner says he accepts the bulk of this material has been shared with security agencies and so he backs the absolute exemption. This appears to impose a blanket ban on the release of SB records, without any need to assess whether it would be in the public interest to do so.
The FOI request in this case was for information on the poet Adrian Mitchell, who died in 2008. It's been reported that in previous decades the Branch had a file on Mr Mitchell's anti-war and CND campaigning.
The latest decision follows several other FOI applications for old SB records, some of which were for information held 20 years ago about the BBC.
In an earlier case about Tony Cliff, the former leader of the Socialist Workers Party who died in 2000, the Information Commissioner ruled last year that SB should release some material it had held about him. This was before the Commissioner adopted his new stance, which was influenced by evidence presented at Tribunal hearings in closed session.
A Met Police spokesperson told me: "The Information Commissioner has indicated that information concerning the work of special branches would relate to, or have been supplied by, security bodies, and would therefore generally attract a Section 23 exemption under the legislation. However, every freedom of information request received by the Metropolitan Police continues to be treated on a strict case-by-case basis."
It is striking to contrast this with the much more relaxed approach adopted by the Police to the disclosure of old SB documentation in the early years of freedom of information. (Of course material relating to existing organisations or living individuals would doubtless still have been a matter of secrecy).
In 2005 I was given access to files that revealed how until the early 1990s Special Branch had infiltrated and monitored the Anti-Apartheid Movement, which campaigned against the South African system of racial discrimination.
Similarly, when I asked SB for information held about the former prime minister James Callaghan, I was sent extracts from his personal protection file. These papers showed that Lord Callaghan felt his level of protection was inadequate, much to the consternation of the Police, as well as providing an amusing account of the "embarrassing situation" when a Jehovah's Witness managed to evade the security precautions at his home.
I can well understand the sensitivity of a personal protection file and, as I wrote at the time, I was surprised by the openness of the Met Police in releasing it.
But looking at the material about the Anti-Apartheid Movement, it is hard to see how it could have any implications for security.
There is nothing in these files to suggest that the AAM was involved in anything illegal, but the documents show how Special Branch's interest in the organisation extended to detailed accounts of routine local meetings attended by six people, reporting on a supermarket worker who handed leaflets to her colleagues at Sainsbury's in Croydon, and investigating a shed found to contain "a large number of political posters with a left-wing bias".
Yet it now seems clear that because of the historically close links between Special Branch and the security agencies, all such material, however harmless and whatever the balance of the public interest, will remain secret in future, despite the existence of freedom of information.