Ballynahinch are now ten points clear of Garryowen with just two games remaining after they defeated Cork Constitution 35-8. Two converted tries inside the opening six minutes saw the visitors build up a 14-3 lead. Gerry Hurley kicked an early penalty for Con' and Eoin O'Donnell scored a late consolation try.
Young Munster bounced back after last week's heavy defeat by Ballynahinch with a 33-12 home win over St. Mary's College. The visitors led 12-11 at the interval Kolio Hifo scored Munster's try and Brian Haugh kicked two penalties. Hifo added two further tries and Derry O'Connor scored a fourth to secure a bonus point victory with Haugh converting two and also adding another penalty.
UL Bohemian were in rampant form on the back pitch at Thomond Park in Division 1B despite getting an early fright when Chris Cousens kicked a fifth minute penalty for Dungannon.
By halftime UL Bohemian led 22-3 with tries by Mossie Lawler, Michael Lynch and Sam Sterling, two of which Robert Burke converted and he also landed a penalty.
The rout continued in the second half with Kevin O'Byrne touching down after only three minutes which Burke again converted.
Glen Sinnamon got in for a Dungannon try which Cousens converted but tries by Lawler and Colin Ryan just at the end wrapped it up for the home side who conceded a penalty try when Ed Kelly was sin binned.
Shannon travelled to Belfast and defeated Belfast Harlequins 16-15. Shaun Horgan scored a try for Shannon which Tadhg Bennett converted and Rob Guerin added three penalties.
U.C.C. moved ahead of Ballymena in to second place in Division 2A after a 17-9 win at the Mardyke. The students trailed 6-3 at half time and Cian O'Halloran's try and four penalties by Sean Og Murphy put College into the promotion spot with just one game remaining.
Richmond defeated Instonians 14-7 at Richmond Park in Division 2B to move into the top half of the table. This defeat means that Instonians will be involved in the relegation play off next month.
Ulster Bank League Division 1A: Clontarf 20, Old Belvedere 13;
Cork Constitution 8, Ballynahinch 35;
Dolphin 26, Garryowen 12;
U.C.D. 21, Lansdowne 17;
Young Munster 33, St. Mary's College 12;
Division 1B: Belfast Harlequins 15, Shannon 16;
Buccaneers 32, Blackrock College 18;
Malone 8, Dublin University 12;
U.L. Bohemian 41, Dungannon 17;
Division 2A: U.C.C. 17, Ballymena 9;
Division 2B: Richmond 14, Instonians 7;