CLONTARF did their part, with Noel Reid's late penalty giving them a 28-27 victory over Lansdowne, but ultimately their race was run a week ago.
At the bottom, Old Belvedere continued their outstanding form to beat Cork Constitution 25-22 at Temple Hill and avoid automatic relegation. It was their fourth win in a row.
They go into a relegation/ promotion play-off game against Division 1B runners-up Belfast Harlequins thanks to tries from Dave Mongan, Dannt Riordan and Leo Auva'a, and 13 points from Gearoid McDonald.
Instead, it is Blackrock who are relegated in last place. They lost 33-27 at home to Garryowen, despite scoring five tries. Shannon stayed ahead of the bottom two by winning 28-3 at Dolphin.
UL Bohemian completed a marvellous late run by winning Division 1B. A 34-14 victory over erstwhile leaders Belfast Harlequins at Annacotty, combined with Dungannon's defeat by UCD, allowed UL Bohs to leap from third to first place.
UCD avoided the drop with a 36-23 victory over Dungannon at Belfield.
Galwegians were relegated along with bottom team UCC after losing 29-20 to Ballynahinch.
Highfield have been promoted to Division 2A, while Ards beat Monivea to stay in senior rugby.