It hasn't happened for 61 years, so the Ireland fans celebrating Six Nations rugby triumph could be forgiven for the heavy heads and bleary eyes they will have woken up with this morning.
Never mind the Guinness-hatted frivolity of St Patrick's Day, this was one gigantic party for anybody in an emerald shirt, as Irish fans celebrated a win against defending champions Wales, which was finally brought about by fly-half Ronan O'Gara, inset below, who scored the deciding drop goal minutes from the end of a nerve-shredding game.
In Cardiff, the scene of the clinching victory in Ireland's first Grand Slam since 1948, pubs were gradually transformed from their normal sea of Welsh red to various shades of green. Many of the revellers behind the gusty strains of Galway Girl and The Fields of Athenry had never seen such scenes.
Randal Stronge, from Belfast, said it was a day he never imagined would ever come. "I'm ecstatic," he said. "This is such a good result for Irish rugby. I have followed them since I was a kid and I always hoped to see this. My father didn't even witness the first one so this is amazing."
The thin margin of victory, just 17-15, made for nail-biting final minutes. Dalkey girl, Caroline Spooner, said: "It was very exciting and it couldn't have been scripted better. The second half was just pure drama. We were absolutely shaking ... I can hardly believe it."
The Irish had descended from Dublin and across the country, some piling into the sun-bathed Welsh capital without a ticket, and prowling the streets for a spare. Fans like Noel Richards, from Limerick. "Myself and my friend, Peter, have been here for a couple of hours," he said. "But it looks likely that we'll have no chance of getting tickets ... they are like gold dust."
But Bernadette Sexton, one of the thousands to cross the Irish Sea without a match ticket, wouldn't let it affect her Cardiff experience. "We'll still have the craic," she said. "I'm planning on watching the game in The City Arms, so we'll be right beside the stadium. In years to come we can say we were in Cardiff. Sure, no one will know if we were in the stadium or not!"
Hugo Lynch, from London, who did see the game, said: "I was bricking myself in the second half but what a way to do it – the best game ever."
In sight of the Millennium Stadium, the Tralee rugby coach, John Murray, savoured the warm-up in the Angel Hotel. "I'm quietly confident," he said. "We have a good solid team, it's going to be close, but we are going to do it."
And, of course, they did. The celebrations were even louder in Dublin as the final whistle triggered raucous scenes and free-flowing Guinness. Pubs were bursting with fans who cheered themselves hoarse.
Irish premier Brian Cowen led the tributes, saying: "Today's triumph will go down in the annals as one of Ireland's greatest ever sporting victories."