The second and third clashes, both in the capital, went Galwegians' way. Again away from home, Galwegians won the fourth and most important one, allowing captain Emer O'Dowd to raise the Paul Flood Cup and carry it beyond the river Shannon.
Speaking after the match, O'Dowd empathised with her Old Belvedere counterparts but congratulated them on their rapid rise through Division 1 ranks in their second season in the premier competition.
"Fair play to Old Belvedere, they play a great brand of rugby and have shown this season and last that you're more than capable of footing it with the country's best," she said.
"Congratulations too to our girls though. We've worked so hard, had our hearts broken a couple of times, but come so far from the start of this season. The Paul Flood Cup is a wonderful reward for a wonderful campaign."
Old Belvedere notched the opening points seven minutes in through a penalty on the 22-metre line, after a furious onslaught from the kick-off.
A poor clearance kick from Old Belvedere gave right winger Sarah Healy and full-back Ali Miller a chance to counter from the halfway mark.
The Ireland-capped Miller broke one tackle and evaded two more to score under the posts after 15 minutes. Out-half Clare Raftery added the extras.
Old Belvedere, so adept this season at retaining possession for prolonged periods, mounted an assault deep in Galwegians territory, three times coming within inches of the try-line.
Galwegians lock Katie McDonagh incurred the referee's wrath and wound up with a yellow card for her troubles.
Despite the player disparity, Old Belvedere could not breach a scrambling defensive unit and minutes before half-time McDonagh's fellow lock Tina Fitzgerald crossed the whitewash to the left of the posts. Raftery's radar was again on target, making it 14-3 for the break.
Whereas Old Belvedere's hopes lay with their forwards, Galwegians' foremost concern for the second spell was to deny the Black and Whites any opportunity deep in blue territory.
Raftery plugged the corners with her educated right boot, and O'Dowd, prop Ruth O'Reilly and replacement Carol Staunton upped the tackle count to snuff out any advances beyond the halfway line.
Galwegians' midfield pairing of former international Nuala Ni Chadhain and Grainne Egan exposed chinks in the Old Belvedere armour, with left winger Lisa McDonagh and Miller reaping rewards with two scything runs apiece.
The visitors' third try came after Raftery shot through a defensive gap, recycled quick ball and Healy dotted down unopposed after slick hands wide out near the right hand touchline. On target, Raftery's conversion just ran out of juice and the score remained 22-3.
Left winger Sandra Gannon, who came on for the injured Lisa McDonagh 22 minutes into the second half, latched onto the end of a classy interchange but was dragged down by desperate defence 10 metres from the line. Full-time came shortly afterwards.