Defending champion John Dunne of Donore ran a smart race to win the men's title at the Dublin Masters' Cross-Country Championships held in a blustery St Anne's Park.
Byrne held back in the early stages, letting Mick Traynor and Brian Leahy of host club Raheny Shamrock and DSD's Peter Matthews set the pace.
He pulled away on the last of four laps for a convincing win, with Leahy finishing second, Matthews third and first M45 and Traynor fourth.
When Dunne, a retired footballer, won the title last year, it was only his third cross-country race. He went on to finish third in the National Masters' Cross-Country and represented Ireland at the British and Irish International in Nottingham last November.
His immediate targets are the National Masters Cross-Country in Tuam next month and a sub-2 hour 30 minute marathon in Rotterdam.
In the women's race, Niamh Fitzgerald of Lucan Harriers, who is the current W40 800m indoor champion, beat Donore's Anne Curley for the title. Fitzgerald, a former international athlete, only returned to racing last year and had warmed up for Sunday's race by winning the first two Meet and Train Winter League races.
Donore made it a men and women's team double in the over 35 age group. On a good day for the club, Donore also made it an over 75 double, with Jim McNamara first of the men and Ann Woodlcok first woman.
Civil Service, led by Grainne Butler, was first W50 team, while Raheny were clear winner of the M50 title.
With masters now outnumbering seniors in Irish athletics, there were record numbers for both races. This is good news for the Irish Masters Athletics Association, which hosts the British and Irish Cross-Coutry International in Santry next November. England traditionally dominate, but Ireland ran them close a few years ago, losing the overall title by only two points.
Last November, the Irish team strung together an encouraging number of strong second places in a variety of age groups.
"We have good individuals, but we can struggle to make teams at international level," says Mick Traynor, a stalwart of the Irish team for many years. "However, we think we have a great chance this year and we're determined to get the best possible teams out in all age groups."
Irish teams are also expected to compete in the forthcoming European Masters Indoors in Torun, Poland from March 23-28. Closing date is January 18; see www.irishmastersathletics.com.