POTENTIAL  attackers of royals would gain a “mosaic of information” if the cost of protecting them is revealed, a tribunal has been told.

The Guardian newspaper is challenging the Government after it did not disclose how much is spent on the royal family’s security following a freedom of information (FOI) request, arguing the amount is of public interest.

Concerns about national security were raised by the Home Office, which does not dispute there is public interest but says revealing information means a higher likelihood of attacks on high-profile figures.

Judges on the tribunal being held in central London will decide if the cost of protection can be disclosed for the first time.

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An FOI request, which gives the public access to documents held by authorities, sent by journalist David Pegg in June 2022, sought a “single, total aggregate figure” for the cost of security provided to the royal family between 2017 and 2020.

The Home Office set out that it does not publicly reveal such information.

In a witness statement, James Rutherford, a senior department official, said: “Protection cost figures for a particular (publicly unconfirmed) set of principals would form part of a mosaic of information which could be drawn together to better allow accurate inferences, and more importantly, increase the confidence of an attacker even without their inferences being accurate.”

He said revealing information would be a “substantial step” in increasing the risk of an attack, enabling “valuable new inferences” about security measures.

Christopher Knight, representing the Home Office, said in his written argument that costs would be “importantly informative” about policing resources and allow would-be attackers “a material degree of educated reverse engineering”.

Stephen Cragg KC, representing Guardian News and Media Limited, argued in legal documents: “Provided that information about the cost of security provision is sufficiently generalised, there is no sound basis for suggesting its disclosure reveals anything significant about the nature of security provided.”

He went on: “Firstly, there is a public interest in a properly informed public discussion and debate about the monarchy. If the public had some sense of what the cost of the royal family to the taxpayer was, it would enable a more informed democratic debate about the British system of monarchy and its costs and benefits.

“Secondly, there are the potentially misleading figures about the cost of the monarchy per person in the UK published in the annual ‘Sovereign Grant Report’, which does not include the costs of addressing ‘physical security risks’.

“As the Appellant (Pegg) says, the publication ‘implicitly accepts that there is a public interest in knowing the cost of the monarchy to the British citizen’ but does not tell the full story.

“Thirdly, there is a public interest in making the royal family more accountable to the British people. The Appellant notes that a recurring theme of reporting on the royal family is the secrecy which surrounds the finances of the royal family, which the disclosure of the requested information goes a way to assuage.”

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The lawyer also said revealing the cost of security would present a “more remote risk” to the safety of the royal family than the detailed publishing of their “future movements,” which do get disclosed.

The Home Office says public interest does not “outweigh” preventing information from getting into the hands of potential attackers.

The two-day tribunal continues.