Clontarf were condemned to only their second defeat of the season by Belfast Harlequins as their lead at the top of the AIL Division One was cut to three points this afternoon.
Ballymena could have knocked the leaders off top spot had they not slipped up to Garryowen by 36 points to 16 in Dooradoyle.
And so it was Lansdowne's overwhelming 40-3 win over Dungannon that made the only inroads into leaders' advantage.
Shannon's slumped further behind after 20-10 defeat to Buccaneers at Ericsson Park while Galwegians kept their play off hopes alive with a heroic comeback against Blackrock College in Stradbrook to win 33-31.
Co Carlow and UL Bohemians, battling it out to avoid relegation, both won to set up a nail-biting finish to the season.
Carlow beat UCD 31-8 in Oak Park while ULB beat St. Mary's 23-17 at Thomond Park.
Division One Results
Belfast Harlequins 24-15 Clontarf.
Blackrock College 31-33 Galwegians.
Buccaneers 20-10 Shannon.
Co Carlow 31-8 UCD.
Dungannon 3-40 Lansdowne
. Garryowen 36-16 Ballymena.
Terenure College 17-25 Cork Constitution.
UL Bohemians 23-17 St Mary's College