Tis the season of goodwill and all that malarkey, but not everyone seems to be in the festive spirit.

A feud has erupted between MMA star Conor McGregor and comedian/radio DJ PJ Gallagher after McGregor took a potshot at Gallagher on Twitter.

The beef seems to have stemmed from a comment that Gallagher made on Twitter, after an American sports presenter mistakenly named McGregor as one of the 'top five active UK fighters in the UFC'. When it was pointed out that he was Irish, she quickly rectified her mistake but Gallagher commented, saying "Normally this kind of thing winds me up but they can have this lad."

McGregor clearly got wind of the jibe and held his tongue until yesterday, when he took to Twitter to blast Gallagher - who has been admirably open about suffering from mental health issues in the past.

Gallagher had been speaking in the media about getting treatment in St. Patrick's Hospital a year ago, and in a now-deleted tweet posted in the early hours of Sunday morning, McGregor said: "@pjgallagher you little sad pox of a thing. Sit up right and smile for a change will you, you sad c*** hahahaha wife left you an all and your crying in the paper bout depression, posture like a prawn. Sad Bastard. I am Ireland. Don't forget it. There's blood on my flag useesoo."

When he was reprimanded by other Twitter users for the outburst, he replied: "Just countering his insults to me that's all. If a supposed advocate for mental health can direct unwarranted vitriol towards me online, then don't cry when it comes back. I am Ireland. I am Dublin. Through and Through. Born and bread. Raised my flag on the highest stage."

To his credit, Gallagher responded with humour in a (now also deleted) tweet that joked: "Excuse me! It took years of hard work and awkward walking to get the posture of a prawn. I am delicious!"

McGregor continued to make jibes throughout the day, including what appeared to be a thinly-veiled threat...

Now, even Irish football legend Paul McGrath has weighed in on the debate in support of Gallagher:

McGregor replied to McGrath's invitation by saying "Paul, you English man" - which he has since deleted.

There have been no further developments since yesterday evening, but watch this space...