Republic has staged a protest inside the grounds of Windsor Castle, calling for an end to “royal secrecy”.

Two members of the anti-monarchy campaign group, wearing black bandit eye masks and golden “crowns”, unfurled a black banner reading “End Royal Secrecy” in front of the famous Round Tower, where the Royal Archives are housed.

Chief executive of Republic which calls for an elected head of state Graham Smith said: “Windsor Castle is ground zero for royal secrecy.

“This is where the Royal Archives are hidden away. That’s why we’ve protested here today.”

He added: “The royals are very secretive. They have persuaded the Government to exempt the monarchy from freedom of information laws.”

He also criticised the manner in which royal wills are not published.

After the death of a senior member of the royal family, it has been convention for more than a century that an application to seal their will is made to the president of the Family Division of the High Court.

This means the wills of senior members are not open to public inspection in the way a will would ordinarily be.

This has made the anti-royalist group question why there are so many things an "ordinary" person must endure with regard to privacy matters that the Royal Family simply does not have to.

Mr Smith added: “Experience tells us the royals will fight to protect their secrets at all costs. They know that their archives and correspondence will shock the public.

“That’s why royal secrecy is an issue that won’t be solved by reform.

“The monarchy must be abolished in favour of an accountable, transparent, elected head of state.”

Republic suggested an increasing number of journalists, academics and researchers were questioning why so many records are kept hidden away.

The Royal Archives, established in 1914, are a unique collection of documents relating to the history of the British monarchy over the last 250 years.

It preserves the personal and official correspondence of monarchs from George III onwards, such as diaries and personal letters.

Access to the Royal Archives is granted solely at the discretion of the Keeper of the King’s Archives.

In recent years, Queen Victoria’s journals were made available online, and the Royal Archives have been working to digitise others papers including records from the Georgian period.

The Freedom of Information Act 2000 does not apply directly to the royal household, as it is not considered a public body.