Review of the AB series

FOI request reference: CAS-66289-M4S6D6
Publication date: February 2021

I’d like to submit an FOI into information pertaining to the timeline of the AB series.
A) Has the MOD indicated when their review might be finished?
B) When did the MOD/NDA initially ask for the files to be closed?
C) What justification did they give? Can you provide evidence of this – correspondence for instance?


The National Archives (TNA) holds information relevant to your request. We are pleased to be able to provide some of this information to you. Some information has not been provided under Part C of your request as it is considered exempt under three exemptions: section 24 (National Security), section 36 (Effective conduct of public affairs) and section 40 (Personal information). We have explained below why these exemptions apply and to what information; redactions made to the released correspondence are accompanied by the specific exemptions.

A) Has the MOD indicated when their review might be finished?

The Ministry of Defence (MOD) has not provided TNA with a date by which their review will be finished, and there are no plans to release a schedule of files yet to be reviewed. Therefore, TNA does not know when the review will be finished. However, where individual records can be returned to public access before the end of the full review, they will be. The MOD may hold the information you have requested. More information on the MOD’s review of historic files relating to the UK’s Nuclear Weapons programme can be found at the following link, including details of the different stages of review being carried out:

B) When did the MOD/NDA initially ask for the files to be closed?

The AB series was withdrawn from public access on 21st November 2018 in response to a letter from NDA dated 16th November 2018. This is a temporary withdrawal and the files are not ‘closed’. Instead, the access status of files within the AB series has been changed to ‘access under review’ while the review takes place.

C) What justification did they give? Can you provide evidence of this – correspondence for instance?

Please find attached a digital copy of relevant correspondence sent by the Nuclear Decommissioning Authority to The National Archives concerning the temporary withdrawal of the AB series from public access. Some of the information within this correspondence is considered exempt under sections 24(1), 36(2)(b)(i), and 40(2) of the Freedom of Information Act and has therefore been redacted. For further information about why these exemptions have been applied please see the explanatory annex at the end of this letter.

Exemptions applied.

Section 24 – National security
Some information has been removed from the letter under the qualified exemption at section 24 of the FOI Act. Section 24 exempts information from release if the exemption is required for the purposes of safeguarding national security. This exemption has been applied to a small amount of information within the letter which discusses the reasoning behind the withdrawal of the AB series by the MOD and NDA, namely due to concerns surrounding its public availability. We are required to conduct a public interest test when applying any qualified exemption. This means that after it has been decided that the exemption is engaged, the public interest in releasing the information must be considered. If the public interest in disclosing the information outweighs the public interest in withholding it then the exemption does not apply and the information must be released. In the FOI Act there is a presumption that information should be released unless there are compelling reasons to withhold it.

There is a general public interest in disclosure of information and we recognise that openness in government may increase public trust in and engagement with the government. Furthermore there is a specific public interest in members of the public being able to understand matters relating to the UK’s national security. Following consultation with subject matter experts within the Ministry of Defence and Nuclear Decommissioning Authority, we have found that the potential consequences of releasing the redacted information would significantly damage the UK’s ability to safeguard national security. There is a strong public interest in maintaining the safety and security of the population by not releasing into the public domain any information which could prejudice national security. For these reasons TNA have concluded that the information is properly exempt under section 24(1) of the Freedom of Information Act.

Further guidance on section 24 can be found here:

Section 36 – Prejudice to the effective conduct of public affairs
Section 36(2)(b)(i) is a qualified exemption which exempts information from release if, in the reasonable opinion of a qualified person, the disclosure of the information would, or would be likely to, inhibit the free and frank provision of advice. With the agreement of the Qualified Person (for The National Archives this is our CEO and Keeper), in whose reasonable opinion this exemption is engaged, the public interest has now been concluded and the balance of the public interest has largely been found to fall in favour of withholding the information covered by the section 36(2)(b)(i) exemption. Considerations in favour of the release of the information included the principle that there is a public interest in showing a true and open account of government decision-making, making for greater accountability and increasing public confidence in political life. However, through consultation internally and externally, we have established that providing the requested information in its entirety would have a detrimental effect on the ability of government department to provide free and frank advice.

It is important that colleagues across government are able to exchange views freely and frankly and to fully discuss any issues that affect this process. The National Archives is required to engage freely and openly with departments on an ongoing basis to discuss the sensitivities relating to our collections. We need the space to have the necessary conversations; and the removal of this space may have an adverse impact on the willingness of departments to provide The National Archives with the level of detail which the process requires. To release some of the information requested may act as an inhibitor to necessary discussions which would not be in the public interest and would be likely to prejudice The National Archives’ ability to carry out its obligations under the Public Records Act 1958 and the Freedom of Information Act 2000. As such, release of this information would be seen to prejudice the effective conduct of public affairs and outweighs the benefits of disclosure at the current time. Consequently, section 36 is considered to be engaged.

Further guidance on section 36 can be found here:

Section 40(2) – Personal information
Data Protection Legislation prevents personal information from release if it would be unfair or at odds with the reason why it was collected, or where the subject had officially served notice that releasing it would cause them damage or distress. In this case the exemption applies because this information represents the personal information of junior members of staff at government departments. Publishing the names and contact details of junior members of staff is considered an unfair use of personal data. Junior members of staff would have no expectation that information about their positions would be made available in the public domain; to do so would be unfair and contravene Art. 5 of the General Data Protection Regulation. As such, the names, positions and contact details of junior officials are withheld under section 40(2) of the FOI Act.

Further guidance can be found at: