The crucial moment of a hard-fought RBS 6 Nations encounter came with Ireland leading 13-9 in the 50th minute when Wales hooker Matthew Rees took a quick lineout and the scrum-half raced away to score in the corner.
But TV replays showed that Rees had taken the lineout with a different ball to that kicked out of play by Ireland replacement Jonathan Sexton, something which is not allowed under IRB regulation 19.2.
Referee Jonathan Kaplan asked his assistant, Peter Allan of Scotland, whether the ball used was the same as that which left the field and, when he answered in the affirmative, the try was awarded.
Kaplan was not able to call on the video referee to adjudicate as the TMO is only to be used for decisions on the act of scoring.