A bride and groom did not know where to look after the best man shared an X-rated anecdote as part of his speech at their wedding.

To make matters worse for the embarrassed couple, the raunchy gag and their red-faced reaction to it has since gone viral after a clip of the joke was shared to TikTok by We Are One Wedding Films. At the time of writing, the video has been viewed 5.9 million times on social media.

Best man speeches are an art form, but there are some basic principles that can help even the most unpolished of orators.

According to Dominic Bliss, the author of the book Being the Best Man for Dummies, one of them is to avoid any jokes at the expense of the bride. "Make jokes about the groom, but leave his new spouse alone," he told The Knot, explaining it is better to keep "any teasing" focused on the groom, who the best man will be likely "closer to."

That memo clearly didn't reach Derek Currie from Perthshire in Scotland.

When he was enlisted to serve as best man at the wedding of Gary and Kirsty Currie, as per the Daily Star, he opted to take no prisoners when it came to his speech.

The result was a gag that featured what We Are One Wedding dubbed "Probably the best punch line from a best man" they had ever seen.

It can be watched in all its glory here.

Reading from a pre-written speech, Derek told the assembled guests about a memorable Christmas when he came downstairs to open his presents only to be greeted with a slap from his mum who scolded him, saying, "What have I told you about bringing folk back here?!"

Confused, he replied: "What are you talking about ma? I'm in my bed the full night."

At this point he reveals that, of course, it eventually transpired that it was his brother Gary, "the golden child", who had someone staying over in his room—none other than his future wife, Kirsty.

Derek went on to share how he and his family began to hear a strange "rustling" sound coming from another room, so he decided to investigate. Heading upstairs, he recalled the moment he flung open the door to Gary's room only to find Kirsty laying there "with her legs at ten and two."

Cue uproarious laughter as both Gary and Kirsty grimaced at the memory of what was likely the most embarrassing moment of their shared lives together—until now.

To add insult to hilarious injury, Derek concluded his story with the amusing quip: "She certainly never came down the chimney in that position anyway. Merry Christmas, Kirsty."

Told in front of the bride's father and with the groom desperately trying to cut the story short while also laughing uncontrollably, this kind of gag might have gone badly in other circumstances, but the combination of Derek's comic timing and Scottish accent made it a winner.

Fans on social media certainly thought so.

Ladyluck loved the bride's reaction, noting: "she was mortified" by the "ten and two" comment. Speelingmistake agreed that the happy couple's reactions were brilliant. "The absolute FEAR in the groom's eyes there," they wrote. "That's when you know a speech is about to be good."

JWakey88 commented: "The Scottish have a way of telling stories that isn't matched anywhere" while CatMolver said it was "So much better when the best man actually tells proper joke stories."

Emilyyay77, meanwhile, paid tribute to the bride for taking it all in her stride. "She's a good team player," she said. "Loved the way the bride laughed it off. I would too but I would have been dying."

Newsweek has contacted the original poster for comment.

A bride and groom at their wedding.
One happy couple's "mortified" reaction to an embarrassing best man story has gone viral. Stock image of a bride and groom at their wedding. prostooleh/Getty