King Charles’s invitation to stay the night at Windsor Castle has been snubbed by Sinn Fein’s first minister in Northern Ireland.

Michelle O’Neill was asked to attend a private dinner hosted by the Monarch before spending the night along with Keir Starmer and other leaders of the devolved nations.

Ms O’Neill has been slammed for the decision, with one Unionist source telling the Telegraph: “You can’t claim to be the First Minister for all and then snub the King.”

The leaders of Northern Ireland, Scotland, Wales and England were asked to join the King for a dinner at Windsor Castle on Wednesday, with some staying overnight and being treating a royal breakfast the following morning, as per GB News.

While Sir Keir Starmer, Scotland’s First Minister John Swinney, and the First Minister of Wales, Eluned Morgan, are still expected to attend, there will be one chair empty at the dining table – though the reasons behind Ms O’Neill’s snub remain unclear.

A spokesperson for the Northern Ireland executive declined to comment but a source told The Telegraph that the refusal may have followed pressure from the minister’s Republican support base.

She has been Vice President of Sinn Fein, once the political arm of the Irish Republican Army (IRA), since 2018.

Relations between the Royal family and Northern Ireland have been amiable in recent years, however, with Ms O’Neill attending both Queen Elizabeth II’s funeral and King Charles’s coronation.

While reluctance to attend a “sleepover” in Windsor may be a far cry from IRA plots to assassinate royals at the peak of the Troubles, it could indicate a tipping point for friendliness between the two factions.

Traditionally a militantly nationalist party, Sinn Fein continues to campain for an independent Northern Ireland, complicating the prospect of close ties with other UK leaders and the Royal family.

The King’s invitation to Ms O’Neill indicates a desire to consolidate close ties with Northern Ireland, pursued by the late Queen and her son alike despite close family member Lord Mountbatten being killed by the IRA in 1979.

“I can’t recall any occasion on which the Sinn Feinn leader would have been an overnight guest of the monarch since the Troubles,” Joe Little, managing editor of Majesty magazine said.

“It is a very magnanimous gesture on the King’s part, rather following in his mother’s footsteps.”