Mary’s clung on for only their second win of the league run thanks to some heroic defending.

Leinster’s Jonathan Sexton kicked an early penalty before a series of scrums led to Hugh Hogan notching Mary’s only try, 15 minutes in.

Shannon captain David Quinlan touched down soon after, but Andrew Thompson’s 51st-minute penalty was the game’s only other score.

Shannon lost their grip on their 100% start to the league campaign as Mary’s, thanks to a superb effort from their forwards in defence and attack, deservedly took the plaudits.

Munster’s most successful league club ventured to Dublin looking to chalk up their sixth straight win of the campaign but Mary’s had other ideas and a first half try from powerful back rower Hogan propelled them to a 10-8 victory.

In awful conditions, Mary’s and Leinster star Sexton in particular, who stepped in for Frank Lynch at out-half, used the wind to heap pressure on the Division One leaders.

Sexton, who was influential as a replacement in Leinster’s recent win over Munster, kicked a ninth-minute penalty for Steven Hennessy’s side and Hogan’s try followed six minutes later.

It came from a bout of pressure near the Shannon try line as Mary’s built up a head of steam with three successive scrums and from the final one, Hogan managed to pile over from close range.

Shannon’s response was immediate though. They kicked a penalty to touch and a quick maul drive put number 8 and captain Quinlan over.

10-5 is how it stayed until Shannon centre Thompson kicked his only penalty, which moved him closer to Eric Elwood’s all-time AIB League record points tally. Thompson started the season 65 points behind the former Galwegians and Connacht out-half – he is now only 20 points worse off.

The visitors looked for a late push and did have the better of possession and territory in the second half, but Mary’s defence was resolute, with the Sweeney brothers Richard Robert in top form, and they deservedly held on for only their second win this season.

Scorers: St Mary’s College: Try: Hugh Hogan; Con: Jonathan Sexton; Pen: Jonathan Sexton

Shannon: Try: David Quinlan; Pen: Andrew Thompson