ROBERT HARDMAN: Today the King will fly into a Caribbean storm over slavery reparations. So can he avert a full-blown crisis?

As royal headaches go, the coming days could make Andrew Mountbatten-Windsor or the daily dramas chez Sussex look like welcome distractions.

Today, the King embarks on a Caribbean tour which will require all of his considerable diplomatic powers. But will it be enough to avert a proper constitutional crisis?

For he finds himself stuck in the centre of an emotionally charged debate on colonial legacy. He arrives as King of several ex-colonies, as Head of a Commonwealth comprising many more and also as Supreme Governor of the Church of England.

The latter is now bitterly divided over paying upwards of £100 million in compensation for disputed slavery links.

With crumbling buildings, many debt-laden parishes are up in arms against a Church establishment now being advised by a 'lawyer-activist' who describes herself as a 'Pan-Afrikanist [sic] and ourstorian' in favour of 'revolutionary warfare'.

The principal bone of contention is whether the King should issue a formal apology for Britain's role in the slave trade.

Aside from the question of whether someone can apologise for something they did not do 250 years ago – and the King has repeatedly voiced his sorrow for the 'horror' of slavery – everyone is acutely aware that an apology would be a cliff-edge moment.

For it would set in motion a legal liability juggernaut involving claims for up to £18 trillion and an international diplomatic pile-on against the UK with one guaranteed outcome back in Britain: a serious blow to community cohesion.

Charles and Camilla pose for photos during a Caribbean tour in 2019

Guyana's President Mohamed Irfaan Ali (left) has urged King Charles to issue an 'apology' over slavery

Hence Andy Burnham's position that he will advise the King to do no such thing. However, in many of those nations calling for an apology, he is their King, too.

It is all very well for the monarch to deflect any awkward questions to his British Prime Minister and his Foreign Secretary. But what if, say, the King's Jamaican prime minister formally advises the King of Jamaica to say sorry?

The monarch will then face a genuine constitutional crisis.

The tour kicks off tonight in the Bahamas (he is King there, too) where the PM Philip Davis has previously called on Britain to have a 'come to Jesus' moment and face up to its colonial obligations.

The King moves on to Guyana, a former British colony which gained independence in 1966 and then swapped the late Queen for a president in 1970. 

Affection for the Royal Family remained, as I saw for myself covering the late Queen's state visit in 1994 when the 25-mile route from the airport into the capital Georgetown was packed with wellwishers.

Returning with Prince Charles in 2000, I saw him treated as an environmental hero (this is one of the most densely forested nations in the world). 

Its current president, Irfaan Ali, has long praised the King's work in that regard.

Yet Mr Ali has now declared that Britain must acknowledge 'the underdevelopment that took place as a result of slavery' and says: 'Moving to the apology is the next step.'

The tour concludes in Antigua and Barbuda, where the King will open the summit of 56 nations of the Commonwealth.

The Royal Family remains very popular in Antigua. The long-serving governor-general Sir Rodney Williams is an old friend of the King and Queen.

The prime minister, Gaston Browne, however, is the man who will be hosting the summit and he has pledged to put 'reparatory justice' at the top of the agenda. 

Furthermore, to considerable surprise within royal circles, the new secretary-general of the Commonwealth, Shirley Botchwey, has lent her support for an apology. 'It wouldn't hurt to have that,' she told Sky News. 

Indeed, she went further by supporting the idea of 'financial reparations or reparations in kind'.

As an ex-foreign minister of Ghana, Ms Botchwey is at odds with her old boss, former Ghanaian president John Kufuor, who has always been very wary of demanding apologies. 

'I assure you, if you come to Africa you will see that there were some very local participants in the [slave] trade,' he has said. 'So we have to be careful.'

Ms Botchwey's remarks also run counter to her previous messaging that member states must look forward if the Commonwealth wants to be relevant.

A one-time powerhouse in the vanguard of dismantling white rule in Rhodesia and apartheid in South Africa, the Commonwealth has done nothing of note in recent years.

Since it includes almost a third of the world's population, every faith across every continent and nations both vast (India) and tiny (Tonga), it has a unique voice. 

With a shared language, plus common legal and parliamentary systems, it is a great network, which is why so many nations still want to join and why its business and civic conferences are always packed.

Yet, at governmental level, it struggles to be taken seriously. As one Commonwealth insider has told me, the British Foreign, Commonwealth and Development Office (FCDO) has 'long forgotten what the C stands for'.

However, it could still be a formidable 'influencer' on issues such as climate change, debt relief and Chinese imperialism if it got its act together.

The Council of Geostrategy, a think-tank on UK foreign policy, has just published an intriguing paper showing that 2027 could be a golden opportunity for the Commonwealth.

Next year, Britain assumes the presidency of the G20 group of top economic powers. The UK is one of five Commonwealth nations in the G20 (with Australia, Canada, India and South Africa).

It just so happens that two other major blocs – the Association of Southeast Asian Nations (ASEAN) and the African Union – also have a Commonwealth nation at the helm next year (Singapore and Ghana).

In his paper, the think-tank's Francis Shin says that if the Commonwealth and Andy Burnham were to use this month's summit to assemble a 'C7' of key Commonwealth nations, it could speak with great global authority on so many key issues.

What's more, just as Canada is seeking associate membership of the European Union, some Commonwealth institutions are welcoming new blood, too. 

Just last month, the Commonwealth Parliamentary Association voted to award Special Observer Status to Ukraine.

What might follow on from that? After all, five nations, including Rwanda, have joined the Commonwealth despite never being part of the British Empire.

All of which could be serious, substantive issues at the Antigua summit, if the delegates were not busy denouncing the evils of slavery. It is a point on which no one could possibly disagree, whereas deciding, two centuries later, on who should now say and pay what to whom is a point on which no one will ever agree.

Some will ask why the King's Government refuses to apologise for Britain's slavery links when the King's Church is not only apologising but pledging £100 million to Caribbean organisations.

Called 'Project Spire', it is the Church of England's atonement for owning shares in an 18th-century fund with slaving links, though the investment is contested. 

A group of clergy have launched a legal challenge, arguing that the Church was actually invested in a different fund and that its money should be spent on churches.

The Guardian newspaper has now accused these opponents of being part of a sinister Right-wing plot to bring down Project Spire.

Perhaps its scrutiny might be directed towards the 'oversight committee' which the Church commissioners have appointed to supervise their £100 million pot. 

They include British-born 'jurisconsult reparationist' Esther Stanford-Xosei, who advocates 'a new international political and economic order' to ensure redistribution of wealth and to prevent 'neocolonialism'.

So how will the King navigate all this?

Given that he has known the modern Commonwealth and its ways for longer than anyone alive (he met many of its founders as a small boy), my hunch is that his charm will prevail and the leaders will not want to embarrass him.

If they try, it could propel a once-mighty organisation ever closer to obscurity and oblivion.