Young Munster completed a stunning finish to the Ulster Bank League's regular season as they squeezed through to the Division 1A play-offs by beating table toppers Lansdowne 15-5 at Tom Clifford Park.

John Staunton's men prevailed in a thrilling battle for the fourth and final semi-final spot, edging out four other clubs who had a mathematical chance of making it through on the last day.

Munsters really timed their run to perfection having been ninth overall in late February. They then embarked on a run of wins over Dolphin, UCD and St. Mary's College before coming good against the league leaders when it mattered most.

Ironically, Young Munster and Lansdowne will meet again in two weeks' time in the semi-finals where Mike Ruddock's men will have home advantage on the Aviva Stadium's back pitch, while the other play-off tie on Saturday 25 April is an all-Dublin affair between Terenure College and Clontarf at Lakelands.

The Cookies will go into that game with a degree of confidence after beating Ruddock's side today and also testing them in a 28-21 defeat at headquarters back in November. Their latest clash was rather listless until late on in the first half when Lansdowne prop Adam Boland was sin-binned.

Boland was scarcely off the pitch when Young Munster's powerful pack capitalised. With a combined effort, they drove over the Lansdowne line and prop Paul Allen touched down. Gearoid Lyons, the place-kicking centre, added the conversion for a 7-0 half-time lead.

The Young Munster faithful were delighted to see their side tag on another try early in the second half. Promising winger Diarmaid McCarthy raced clear from near halfway for a fine opportunistic score to give his side a 12-point advantage.

The return of Boland steadied Lansdowne and, with 21 minutes left on the clock, they got back within striking distance thanks to an unconverted try in the corner from scrum-half Paddy O'Driscoll.

However, with results elsewhere going their way, Munsters made sure of their fourth-place finish with a well-struck 77th minute penalty from Lyons.

Meanwhile, Ballynahinch, who entered the final round in fourth spot, must be sick of the sight of Clontarf. The north Dubliners won the sides' recent Bateman Cup semi-final and they returned to Ballymacarn Park for a 33-18 bonus point league victory.

'Tarf, who also beat 'Hinch twelve months ago to claim the league title, made the early running with tries from number 8 Anthony Ryan and recent Ireland Under-19 cap Conor O'Brien, who joined the experienced Evan Ryan in the centre.

Outside-centre Steve Macauley cancelled out a David Joyce effort to give Ballynahinch some hope at the break, trailing 17-8, and they reduced the arrears to 20-18 thanks to scores from influential duo Michael Graham and Rodger McBurney.

However, Andy Wood's charges replied with an Adrian D'Arcy try which full-back Rob Keogh converted. The latter went on to play a crucial role in seeing out the win, slotting two final penalties to give his side a 15-point winning margin.

UCD held onto their Division 1A status with a well-earned 10-3 triumph away to Cork Constitution, who face Clontarf in next weekend's Bateman Cup decider.

The students may have finished two points away from a semi-final berth, but maintaining their presence in the top flight was all that mattered in a nervy encounter with the Leesiders.

In windy conditions, a lone penalty from returning Ireland Under-20 out-half Ross Byrne split the sides at half-time in Temple Hill. Neither side had won in the league's past three rounds, so prop Liam Hyland's second half try looked like being a vital score for the students.

That proved to be the case as Constitution could only answer back with a single penalty from young out-half Tomas Quinlan, as Tom Tierney's side ended up finishing just one point above the promotion/relegation play-off spot.

St Mary's will have to contest that play-off, having home advantage against Division 1B runners-up Garryowen on April 25, as their 45-18 thrashing of already relegated Dolphin made no difference to their final league placing of ninth.

Mary's ran in seven tries with their five-try second half haul including scores from Rhys Ruddock's brother Ciaran, league debutant Terry Kennedy, a brace from man-of-the-match Conor Oliver and winger Ryan O'Loughlin dived over late on to close out the scoring.

At Anglesea Road, Old Belvedere's push for the play-offs came up just short despite a hard-fought 18-8 win over second-placed Terenure. 'Belvo finished fifth overall - a single point behind Munster - after winger Josh Glynn landed six of his seven penalty attempts.

Glynn punished Terenure's indiscipline with the visitors have hooker Robbie Smyth sin-binned before the break, and flanker and captain James O'Neill also saw yellow in the second period.

'Nure were 12-5 behind at half-time having scored the game's only try, a long clearance kick bouncing in their favour and quick hands released centre Stephen O'Neill for an unconverted score.

Old Belvedere boss Paul Cunningham will rue his side's missed try-scoring chances when reviewing the video - the best of them saw Glynn knock on close to the line and lively flanker Kieran O'Gorman was held up short from a lineout move.