An influential British think tank has urged the British government not to go ahead with a UK-wide festival in 2022 because it clashes with the centenary of partition.

At the Conservative Party conference last October, British prime minister Theresa May announced there would be a year-long Festival of Great Britain and Northern Ireland in that year.

It would be similar, she suggested, to the 1851 Great Exhibition in London or the 1951 Festival of Britain and was envisaged as a “showcase of what makes our country great today”, Mrs May said.

Sunder Katwala, director of the British Future think tank, said the whole process appears to have been derailed by the protracted negotiations over Brexit.

He said the festival will coincide with significant and controversial centenaries including the foundation of the Irish State in 1922, which copperfastened partition following the Government of Ireland Act 1920, and the foundation of Northern Ireland in 1921.

“The specific coincidence with the politics of Irish history and the politics of Brexit means you are not going to have a festival which works across the nations of the UK and across communities in Northern Ireland,” he said.

In any case, he believes 2022 is too early to host such a festival. “It would take them at least three years to get it right. You could hold it successfully in 2025,” he said.

British Future examines issues of British identity and culture. It produced a report for the British government on the effectiveness of the country’s first World War commemorations between 2014 and 2018.

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Mr Katwala, whose mother is from Midleton, Co Cork, said the Irish Decade of Centenaries had been conducted successfully to date because it had sought to acknowledge that “moments that are potentially divisive are also potentially important”.

Mr Katwala pointed to a recent controversial interview with the conservative thinker Roger Scruton who referenced Taoiseach Leo Varadkar as a “Hindu immigrant”.

Mr Katwala added: “It betrays a lack of understanding of Irish history. The British-Irish relationship between 1986 and 2016 is probably the most successful three decades of intergovernmental relationships that we have ever had. We are letting that fray a bit and relations have become a bit of a pawn in the frustrations over Brexit.”

Prof Sir Hew Strachan, one of Britain’s best known historians, said proposals to extend public commemorations of the first World War to include events afterwards such as the Irish War of Independence never got far.

Sir Hew was a member of the UK advisory committee on the first World War which he described as another casualty of Brexit.

A debrief that was scheduled to discuss how the first World War centenary had gone and what should follow was never held.

Sir Hew said some members of the committee were keen to extend the centenary commemorations to embrace Britain’s imperial obligations after the war, which included Ireland, India, Mesopotamia, Iraq and Egypt – all which proved to be troublesome regions.

“The fighting didn’t just stop in November 1918 as Ireland knows only too well. The view of the Government as expressed by ministers and Andrew Murrison (British prime minister’s adviser on commemorations) for the First World War was that getting to the finishing line of November the 11th was about as much as they had stamina for,” he said.

“We never got as far as Ireland. There are issues that are potentially instructive about the complexity of war and peace. Ireland exposes all of that. I think they (the British government) will find it difficult because it is politically difficult for them today.”

Sir Hew said the British public was “extraordinarily ignorant” about their country’s imperial past. “They don’t even have a nostalgic view of Empire. They have forgotten they even had one.”

He said British school was “all about the Nazis” and that Britain standing alone in 1940 has been used by Brexiteers in a “contrived and self-selecting way”.

He added: “I say as a historian that there is a lack of historical awareness which is extraordinary when other countries and other peoples have a much greater sense of their own past.

“We don’t have a sense of historical understanding which represents the complexity or depth of any of this. You see it in the cavalier attitude taken towards the Good Friday Agreement and the peace process. They really don’t see how important it is.”