The National Archives are home to more than 11m documents, many of them covering the most disturbing periods of Britain’s colonial past. The uncomfortable truths revealed in previously classified government files have proved invaluable to those seeking to understand this country’s history or to expose past injustices.

It is deeply concerning, therefore, to discover that about 1,000 files have gone missing after being removed by civil servants. Officially, the archives describe them as “misplaced while on loan to a government department”.

The files, each containing dozens of pages, cover subjects such as the Troubles in Northern Ireland, the British colonial administration in Palestine, tests on polio vaccines and territorial disputes between the UK and Argentina. It is unclear whether duplicates exist.

The loss of so many documents of such significance has understandably caused concern among historians, politicians and human rights groups. Amnesty International has called on Theresa May to order an urgent government-wide search for the documents, while Labour MP Jon Trickett has warned that the loss “will only fuel accusations of a cover-up”.

Such suggestions may seem far-fetched, but recent history has given many people reason to be suspicious. Documents in the National Archives have previously been key in revealing human rights abuses by the British state.

In 2014, for instance, investigators from the Irish broadcaster RTÉ uncovered a 1977 letter from the then home secretary, Merlyn Rees, to the prime minister of the day, James Callaghan, in which Rees claimed that ministers had given permission for torture to be used in Northern Ireland during the Troubles. The information had reportedly been withheld from the European court of human rights.

British army soldiers patrolling streets of nationalist west Belfast during the Troubles in Northern Ireland. Photograph: Alain Le Garsmeur/Getty Images

Also in 2014, the government was accused of a cover-up after it said it could not release information about the CIA’s “extraordinary rendition” programme because the files had suffered “water damage” .

In 2013, meanwhile, the Guardian revealed that more than 1m documents that should have been declassified were instead being unlawfully kept at a high-security compound in Buckinghamshire. Their existence only came to light when a group of elderly Kenyans took the government to the high court, claiming they had been tortured during the 1950s Mau Mau rebellion. The Foreign Office was forced to admit it had withheld thousands of colonial-era papers.

Even if the files that have now been reported missing vanished as a result of sloppiness or incompetence rather than malice, that is in a way no less damning. Britain has long failed to acknowledge the horrors that its colonialism and imperialism have wrought on the world.

Many Britons have grown up believing their homeland saved and civilised the world, while atrocities, genocide and human rights abuses often go unmentioned. Successive governments have failed to narrow this knowledge gap, whether by setting up truth commissions, establishing a museum of colonialism or teaching schoolchildren about colonialism as part of the standard curriculum.

In 2014, a YouGov poll found that 59% of those surveyed thought the British empire was more something to be proud of than ashamed of.

The loss of these documents provides an apt metaphor for what colonialism means to many in Britain. Embarrassing facts are neatly filed away, labelled as “the past”, and on the rare occasions that the archives are inspected, damning evidence is nowhere to be seen.

• Siobhan Fenton is a freelance journalist