It comes as Sky News understands that meetings have been held today to discuss what engagements can continue and those that may have to be altered to be more appropriate during the next six weeks of heightened political sensitivity.

Talking about yesterday's statement, Craig Prescott, a lecturer at Royal Holloway University and author of Modern Monarchy, said: "I thought it was odd. I don't remember previous general elections having any statement like this.

"I would have imagined that in previous election periods, they might have taken a view of the proposed engagements and thought 'maybe we don't do that one and that one during the election, and we'll push that back'.

"I think the surprise here is that they've made this statement and are acting so publicly about all this. I think, perhaps under the reign of Elizabeth II, all of this might have been done a bit more discreetly, and we just never noticed it really".

Shortly after Rishi Sunak announced that he had spoken to the King and was calling an election, Buckingham Palace said: "the Royal Family will - in accordance with normal procedure - postpone engagements that may appear to divert attention or distract from the election campaign."

Palace sources are keen to stress there is no variance from what happened at previous elections and like all government departments the palace is now in a "pre-election period of sensitivity".

Suggesting the statement may be because this is the first election under a new monarch, Mr Prescott added: "Charles comes into being King with a track record of being engaged in political issues in broad terms, you know, in a way that Elizabeth II never was, so I think there's perhaps a desire for there to be more caution, about being seen to be involved in political matters.

"And, you know, to make crystal clear there is a line and the King is going to stay the right side of that line."

Sky News understands it also caused disagreements within the royal household about whether postponing engagements was necessary.

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Both the King and Prince William were due to carry out visits on Thursday and the King was due to go to Crewe on Friday, including visiting a charity that helps those struggling financially.

All the engagements for the King and William involved elements about social issues, that some may see as political, but all are topics the monarch and heir have engaged with in the past.

Prince William's visit was cancelled due to "updated guidance" from Buckingham Palace.

Craig Prescott believes it possibly exposes an acknowledgement from the palace that the royals are now straying closer to the political line than they may have done in the past.

"I suppose the other point is that it is in a sense an admission that some of the things that they do are political," he said.

"Because our general view of monarchy is that it does things that are not politically controversial. And this is an admission that they are doing some things that are pushing the envelope a little bit, but this is not to push the envelope".

A garden party for the RNLI still went ahead at Buckingham Palace today. It's understood that all engagements will be reviewed on a case by case basis. Members of the Royal Family will still attend D-Day commemorative events.