In a fleet of 44, including many of the world's top boats, he had already put together a solid series as the final day arrived in the excellent sailing waters off Abersoch in North Wales.
But whether or not he and his crew of Adam Winkelmann and Pedro Andrade came home with bronze, silver or gold, hinged entirely on that last race.
Sailing the immaculate Jaguar, he logged the kind of race that, for most skippers, is the stuff of dreams.
Jaguar emerged clear from the starting melee to such good effect that by mid-race she had a clear lead of 200 metres, a comfortable gap that enabled Byrne to keep effective cover on any challengers, such that the real race was for second place as Jaguar powered on to finish an extraordinary three minutes ahead.
It was textbook stuff. In his winner's speech, Martin Byrne said the secret of it all was the shoreside commander, his wife Triona, who looked after logistics and paperwork, and ensured everything ran smoothly all week.
Irish sailing needs more Trionas.
The Byrne win gives a boost towards 2012, which in Ireland will be the Year of the Dragon. The Edinburgh Cup will be on Belfast Lough from July 4-8, while the historic Gold Cup is in Kinsale from September 8-14.
Ireland has won a dozen Edinburgh Cups, the most prolific victor being Tony O'Gorman who won six times between 1975 and 1984.
But only once has the Gold Cup been brought home, in 1947, when it was won by Eric Strain of Belfast Lough. Robin Hennessy was in the frame in 1971 but didn't quite clinch it, so an Irish win is overdue.
And, with the Gold Cup scheduled for Ostende in September, maybe we won't have to wait until next year.