This is how the Olympic world reveals itself to be a flimsy reality. Paddy Barnes is standing by himself as his coach John Conlan lauds him in an empty marquee behind the boxing arena.

“It’s just devastating, he’s probably been our most successful boxer, I feel,” Conlan is saying quietly, funereally, weighing each word. “This is his third Olympics and I personally felt he was getting a gold medal.”

Didn’t everyone lazily assume that?

But now, suddenly, Barnes is out of the Olympics and is trying to process this cold fact.

Four years of training and plotting and his dream evaporates in a matter of minutes. It is a cool noontime in Rio but the Belfast man is drenched and he looks as drained as a marathon runner and he stands there, as alone as he has ever looked.

Then Samuel Carmona Heredia, the Spanish kid who had kept coming for more during three riveting, merciless rounds, walks by with his coaches. And Barnes has the poise to do something which is as demonstrably classy as anything he has ever done in the ring.

He chats with the victor and they bump fists and then he poses for photographs with Heredia and his coaches. He even manages to smile.

You have to remember that Barnes is reeling just now. He is caught up in Inception: the buildings and frameworks are crashing down about him. He came to Brazil fired with a belief that he could win gold at light fly (46-49kg) level but within three minutes of facing down the furious, opportunistic style of Heredia, a new truth was beginning to dawn on him.

So tired

His body simply doesn’t have the juice to compete at this division any more. All the previous struggles to make the grade on weigh-in day were, in retrospect, screaming advice that he had no choice but to ignore.

Even as he boxed in the cavernous arena in Barra, he knew.

"Just so tired," he said when it was over in direct, unsentimental Belfast-ese. "I feel I'm too big for the weight. There was doubts about me making the weight. Seven weeks ago I was 58 kilos. I didn't think I was going I was going to make it myself but I pushed that hard because it was the Olympic Games. Actually, qualifying for these I didn't make the weight.

“We had to pay a fine because I was over the weight every time so . . . I felt good going into the ring but at the end of the first round my energy was completely gone. I had nothing to give. I don’t know how I threw as many punches as I did in the second and third. I don’t know where they came from because I was so weak.”

Where they came from?

Probably from old voices echoing all the way from the Holy Family boxing club in north Belfast or the countless hours working under Billy Walsh and Zaur Antia and probably too from the thought of his family and friends out in the stands willing him on.

Everyone knows Barnes has a scamp-ish sense of humour in everyday life but in the ring he is solemn as a tax accountant on returns week. His features were pinched and drawn by the end of round one. Maybe in Carmona Heredia’s ambition and energy he recognised some past version of himself in Beijing and in London. He had no choice but to engage the Spaniard in an enthralling bout in which both men looked to exploit every single chance to punch.

“Going into the last round I was told it was level and I thought I won the last round,” Barnes said, not unreasonably. It was a savagely close fight.

“And I am actually happy that he got the decision because the next fight I wouldn’t have lasted like this. I would have been embarrassed and made a fool of meself. I am devastated. I came here for the gold medal and I truly believed that I was going to win the gold. And to be defeated in the first fight . . . it is terrible, like.”

It is that. Ireland had come to see Barnes in much the same way as Katie Taylor: a dead cool, reliable medal contender.

No gimmes

Bronze in Beijing, bronze again in London when the Irish team stormed the boxing arena and flag-bearer at Rio at the age of 29; a statesman with an unquenchable thirst for juvenile comedy.

There are no gimmes in Olympic fighting but Barnes had become such a model of reliability that the truth is, the outside world took this bout for granted. The judges scored it 29-28, 28-29, 28-29 against the Irish man.

“It’s not a shoo-in, I mean every fight is hard. I watched five fights this morning, five tapes of this guy, and I know what he was bringing to the table,” said Conlan.

“I watched him closely in the last few qualifying competitions and he was hard done against an English guy so I knew what to expect. Paddy is saying about the weight and eventually it does take a toll on you. He made the weight bang on 49 this morning, he was hitting hard in the warm-up with the pads and it’s just a little bit too much for him, as he said.

“I’m gutted for him and his family. He’s the life and soul of the camp, Michael [Conlan] was speaking there a couple of seconds ago and said he was devastated. But they’re professionals: they’ll get on with it. They’ll sit down and they’ll joke a little bit about him being the first out, and not welcome back into the room . . .”

And Barnes will take it. He’ll keep grinning. A great Irish Olympian bows out. This day will hurt him for a long, long time.