Last night's Rose of Tralee show was interrupted when the stage was invaded by a man dressed in a priest costume.

The protester in question was Matt O'Connor, the London-based founder of the Fathers 4 Justice group, who had bought a ticket to the event. 

Speaking to Newstalk Lunchtime earlier, Mr O'Connor pledged that it would be the "first of many" Irish demonstrations by the controversial group.

So who exactly are they, and what are they protesting against?

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Fathers 4 Justice (F4J) was founded in 2001 by Mr O'Connor, who says he was denied access to his two boys following a difficult divorce.

While his own case was resolved in courts, the organisation says the wider campaign was "born out of his love for his children, and his fear that one day they might suffer the same injustice as him – what he called a 'living bereavement' – when they became fathers".

The main goal of the group has been campaigning for equal rights for fathers and reforms for Britain’s family justice system.

Over the years they have called for the British government to introduce initiatives ranging from legislation for shared parenting to a dedicated 'Minister for Men'.

Throughout the 2000s, the group started making international headlines with a number of unusual stunts intended to draw attention to their cause.

In 2002, the group carried out what they called their first direct action demonstration, which saw 200 men dressed as Father Christmas "storm" the offices of a British government department.

The group claimed responsibility after Tony Blair was hit with a purple "flour bomb" during a parliamentary debate in 2004.

It was in that same year that the group launched what remains their best known campaign - a series of superhero protests.

The various public protests saw members of the group don superhero costumes in a bid to raise awareness of Fathers 4 Justice and their goals.

In perhaps the most infamous example, one campaigner, Jason Hatch, took to a balcony in Buckingham Palace dressed as Batman (and with a Fathers 4 Justice banner).

Another superhero protest saw a man dressed as Spiderman climb the London Eye for an 18-hour-long demonstration.

Demonstrations in public places has become a key tactic employed by Fathers 4 Justice - with other protests having taken place at the British House of Commons, during the World Snooker Finals, and - now - the Rose of Tralee stage. 

The group's stunts have earned them plenty of media coverage, both in the UK and internationally, while Matt O'Connor himself has published a book described as an "inside look" at the movement.

F4J have, inevitably, attracted plenty of controversy over the years - with many critics denouncing the group's tactics while acknowledging grievances the F4J members face.

The parenting website Mumsnet, for example, responded to the group after F4J released an ad claiming the site "promotes gender hatred" (alongside various other actions against the website).

A statement released on Mumsnet in 2012 argued: "We believe that the issue of a father's access to his children is important and needs to be discussed. We understand that many Fathers 4 Justice campaigners are driven by intense personal anger over what they feel is injustice they have suffered in their own cases.

"But the recent actions the group have taken against Mumsnet and others constitutes plain and simple bullying and intimidation, and only harms its cause," they add.

Members have also faced legal trouble over their actions. In 2014, for example, one F4J campaigner was jailed for defacing a portrait of the Queen.

There has also been some internal strife, with the group having temporarily disbanded following claims that a "dark underbelly" of former members was attempting to kidnap Tony Blair's son.

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As their efforts in the UK continue, F4J launched a campaign in Ireland earlier this year calling for "automatic presumption of guardianship for fathers and ensuring that children can grow up with a dad."

Writing on their website, F4J say their campaigning in Britain "has persuaded politicians from across the political spectrum to accept that shared parenting is responsible parenting, and will lead to better outcomes for our children, our families and our country".

"Matt O’Connor and Fathers 4 Justice remain defiant, committed to ensuring that automatic parental responsibility for dads, and a legal presumption of 50/50 shared parenting and child support, becomes law by the end of the decade," the group adds.