Gerard Kelly may be a mammy’s boy, but that didn’t stop his mam, Mary, from shouting threats at him in the car…all in good fun, of course.

The mother and son duo were on their way to Gerard’s cousin’s wedding where he was expected to sing “In a Country Churchyard” by Chris de Burgh.

Mary reminded him of the lyrics over and over again, but Gerard deviously pretended to mess them up, winding his poor mam up.

The tune they practised was her and Gerard’s father’s wedding song, so she took it to heart when her son just couldn't get the words right.

In a country churchyard there's a preacher ON his people,” he sang aloud.

WITH his people. The preacher’s WITH his people.” She did not cop on to her son’s jokes.

Gerard continued singing more ‘accidentally’ wrong lyrics, and she could not believe he was going to mess up his parent’s song at the wedding.

He was secretly filming her reaction, and Mary finally lost it towards the end of the video.

“If you mess that song up on the altar I’ll go up and bate you over the head with the guitar me-self,” she said with a few more curse words thrown in.

The hilarious video has gone viral, and many comments said that Mary’s reaction was ‘brilliant.’

We wish we could have seen this mam’s face when her son told her he was only winding her up.