THE situation at the top of the Insurance Corporation All Ireland League

Division One table is so tight that by this evening any one of three clubs could be the league leaders, with Shannon, Garryowen and St Mary's College all in contention.

Shannon go into their match against Old Belvedere a Thomond Park in first place, which they took over from Garryowen last week as a result of the win over Old Wesley. Shannon and Garryowen are both on 12 points, with the latter having a match in hand but an inferior points difference. Garryowen make the journey to Lansdowne, who having lost three matches, are out of contention.

St Mary's - on 10 points but with a game in hand on Garryowen and two on Shannon - travel to play Young Munster, who like Lansdowne have lost three matches, but that will not diminish their will to win this one against the side they defeated to win the title in 1993.

The games this afternoon could have a profound bearing on the destination of the title. Not alone, are the top three separated by just two match points, even the points difference is minimal between Shannon and St Mary's. Shannon have a points difference of plus 38 and St Mary's plus 39, while Garryowen stand on plus 24.

Points difference could decree the leadership this afternoon. Were Shannon and Garryowen to lose and St Mary's win then the Dublin club would take over at the top. Were Garryowen and St Mary's to lose and Shannon win, then it would mean all three will have lost two matches and that would make Shannon favourites to retain the title, especially as St Mary's must meet Garryowen and Cork Constitution, who are still in contention having also lost two matches. Constitution will be at home to Ballymena. But with eight points from six matches, a win today irrespective of the results of the matches involving the other contenders will not put Constitution on top. They have a match in hand on Garryowen and two on Shannon. Pride and prestige will be the issues at stake when Blackrock take on Old Wesley in the fifth first division tie down for decision today.

Meanwhile, this afternoon could prove to be the most auspicious occasion in the history of the Old Crescent club. Two points clear of the nearest pursuers Terenure and Dungannon and with a match in hand over both, a victory over Clontarf at Rosbrien would spark loud and protracted celebrations, as Old Crescent will be assured of promotion to Division One. They will thus joins heir Limerick neighbours Young Munster, Shannon and Garryowen for the first time in their history. Old Crescent are unbeaten in the league, having dropped just one point and having played some excellent rugby in attaining that exalted position.

Terenure and Dungannon are both on 11 points - but Terenure have the better points difference. With Terenure not engaged today, Dungannon can take over, second position by making home advantage pay by beating Wanderers, who like Clontarf, are out of contention.

Greystones, are in fourth place and still have promotion ambitions. They are two points behind Terenure and Dungannon but with a match in hand and travel to Gibson Park to play Malone, who are not promotion contenders. Greystones' fate is in their own hands as they have to meet both Dungannon and Terenure in the league, so a win today is imperative. The other ties have no bearing on promotion as Dolphin meet NIFC and Sunday's Well take on Bective Rangers.

There is no disputing the match of the day in Division Three. That is the match between league leaders Monkstown and Highfield at Model Farm Road.

Monkstown lead the league on 141 points, one ahead of Highfield and Monkstown have much the better points difference. As circumstances have it, the third and fourth placed teams City of Derry and UCC, will meet at Judge's Road, while Bohemians in fifth position, like UCC on eight points, travel to Waterpark, who have seven, as have Skerries, DLSP and Buccaneers. With six "clubs due to be promoted from this division, crucial points are at stake today, too, when Buccaneers travel to DLSP and Skerries, meet UCD at Belfield. Galwegians will be seeking their first league win when they take on Bangor at Crowley Park.

Division Four leaders Portadown can strengthen their championship prospects by beating third placed Queen's University at Chambers Park. Dublin University, in second place, will not be playing today as their match against Corinthians has been, postponed. Collegians, who are on the 10 points mark with Queens and Trinity but with inferior points difference, will have home advantage against Ards.