It's not surprising that chess grandmaster Nigel Short was looking a little tired around the eyes.
He had just spent the last few hours playing not one opponent - as is usual in chess - but 40.
That's right - 40 separate opponents.
The extraordinary event was held last night in the Common Room of the Royal Belfast Academical Institution - 'Inst' to most of us - and organised by the Ulster Chess Union.
The atmosphere throughout was hushed and tense.
The blinds in the room were drawn.
Players sat at long trestle tables, littered with half-drunk cups of tea and bun wrappers, their boards in front of them, while Short circled the room, tea-cup and saucer in hand, stopping at each board to make his move.
Some players were very young, others at retirement age, or beyond; some were casually dressed in leisure-wear, others were wearing three piece suits.
One had a jaunty bow-tie.
All of them were male - it seems that chess is still a very masculine game.
Each paid £25 for the privilege of playing against Short.
"What people don't realise is that in the first five moves of any chess game, there are 800 trillion combination possibilities," said Damian Cunningham of Ulster Chess, watching Short in action last night.
"And there are more moves in a game of chess than there are atoms in the known universe."
This makes Short's ability to hold all the positions of each game in his head all the more remarkable.
But then he has impressive form. Now 49, he tied first place at the British championships at the age of 14, and became a grandmaster at the age of 19.
At one point he was ranked third in the world, and he challenged Garry Kasparov for the ultimate title of World Chess Champion.
"And he ran Kasparov close," said Cunningham.
It's fitting that such a big chess event, with players coming from as far afield as Hungary, Poland, Denmark and Egypt, should be held in Belfast.
After all, the first World Chess Champion came from this city.
Alexander McDonnell, from Berry Street, played French aristocrat Louis-Charles Mahé de La Bourdonnais, then known as the world's strongest player, in the summer of 1834. McDonnell won the second match, which is why he became, all too briefly, the world champion.
In Belfast last night, Short acted quickly at times, decisively swooping in to take a piece; other times he stopped to ponder, scratch his head, rub his chin, his hand hovering over the board.
As the night went on, and more and more players were knocked out, Short's circuit of the boards became faster and faster.
But still nobody looked like coming anywhere near to beating him.