THE main challenge to the future of the monarchy is the potential break-up of the union and it could be hard for King Charles to remain neutral in another independence referendum, according to a new analysis.

Professor Robert Hazell, founder and first director of the Constitution Unit at University College London, said a vote for Scotland to become independent would be a “severe blow” for the Royals and it may be difficult for the King to stand “idly by”.

However he said the monarchy would face an even greater risk if it allowed itself to be “co-opted” by Unionist politicians.

While the SNP has pledged to retain the monarchy after independence, he said Scots may press for an early referendum on whether to keep the Royals if they sense Charles’s primary loyalty is to his “larger kingdom”.

The paper published by the Institute for Government as part of a review of the UK’s constitution explores the different challenges for the monarchy following Queen Elizabeth’s death.

Hazell pointed to the tour of the four nations carried out by Charles as the first act of his reign, viewed by some as a bid to save the Union, and questioned whether the monarchy could remain neutral in a second independence referendum.

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“The 2014 referendum was famously an occasion when the Queen’s usually impeccable neutrality seemed to slip for a moment,” he wrote.

“As someone who has been proclaimed King of the United Kingdom of Great Britain and Northern Ireland, can Charles pretend to be unconcerned if he becomes King of a "Lesser Britain"?

“The standing of the monarchy will inevitably be damaged, even if responsibility for the break-up lies with the politicians and not the monarch.

“So it will be hard to stand idly by, but a greater risk to the monarchy would be to allow itself to be co-opted by unionist politicians, as Liz Truss attempted to do when she sought to join Charles’s inaugural tour of the nations.”

Hazell said the pledge by the SNP to retain the monarchy so that Charles will be head of state will be “small consolation”.

“That would be a hard role to fulfil if the break-up leads to a difficult divorce, as with Brexit, with Charles trying to remain above the divisions of his fractious kingdoms," he said. 

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“In addition, the SNP have long had a fundamentalist wing who have no time for the monarchy; if the Scottish people sense that Charles’s primary loyalty is to his larger kingdom, they may press for an early referendum.”

Other challenges identified in the report include maintaining popular support, with lower levels of backing likely to lead to pressure for the government to reduce funding for the monarchy.

The prospect of the 14 countries around the world where Charles is head of state becoming republics – such as Australia, Antigua and Jamaica – is also identified as a potential difficulty.

But the paper notes the monarchy might be “privately relieved” if this happens, bringing a reduction in workload and also getting rid of “reputational risk” involved with some of the “more unstable realms”.

Hazell added: “Fiji has seen four coups d’état in the last 40 years; it must have been a relief to the monarchy when the second coup in 1987 resulted in removing the Queen as head of state.”