After last weekend's victory over France - a fourth on the trot - Ireland's first ever RBS 6 Nations title was secured but it was the Grand Slam they were so desperate to secure, and did so in nail-biting fashion.
Things didn't get off to the best of starts for Ireland, who fell behind after just three minutes - Italy fly-half Veronica Schiavon continuing her impressive tournament with the penalty.
That stirred Ireland into life however and Philip Doyle's side advanced up the pitch, going through the phases well despite the difficult conditions, and earning themselves a 13th-minute penalty.
And Briggs, whose nerveless kicking made sure of the victory over France last time out, made no mistake again to level the scores.
As the half wore on, defences remained on top but it was Briggs and winger Niamh Kavanagh who threatened most for the visitors, just falling short when chasing a kick through.
Ireland survived a major scare midway through the first half when Maria Diletta Veronese broke through the Irish defence and only a last ditch tackle from Alison Miller prevented the opening try of the game.
Ireland did earn a chance to go ahead just before the break, but Briggs was off target with a difficult kick from out wide, ensuring the two teams headed in at half-time level at 3-3.
Ireland were fired up for the second half and they came flying out of the blocks, dominating up front as Italy were reduced to 14 and after moving themselves up field, they won what proved to be the crucial penalty.
Briggs slotted the kick on 50 minutes to give her side the lead but back came Italy who won a penalty of their own on 62 minutes, only to see the kick drop agonisingly short.
Italy, seeking a third win which would move them up to third, continued to exert pressure, forcing Ireland into some resolute defence of their try-line as the clock ticked down.
Irish hearts were in mouths when Italy were awarded a late penalty from a scrum, but the hosts chose to kick for the corner and the visitors held firm to send their travelling fans into rapture.