Robertson Spuddies won the third grade premiership on Sunday, beating the undefeated Mt Warrigal side to bring home the trophy.

It was the first premiership for Robertson in Group 7 and the first since their 2013 title.

The Spuddies had faced Mt Warrigal- a team that had won the past three premierships- twice throughout the year and on both occasions, were unable to get the win.

But an 18-10 victory handed Robertson the premiership and Mt Warrigal their first loss of the season.

"We are very much over the moon," captain/coach Damien Barton said.

"It [the premiership] means everything. We knew we had a team that could do it. We went down there with the right attitude yesterday and came home with the trophy."

Barton said defence was the key to the Spuddies victory.

"We've been working on our defence all year."

While the Spuddies had plenty of ball early on, it was Mt Warrigal that jumped out to an early lead.

But Robertson dug in, refusing to be kept out of the game and scored three tries in the second half (James Foyer, Harry Whatman and Barton) with Josh Heyhorn kicking all three conversions.

"Everyone played above what they usually played," Barton said

Robertson's Jayden Valenzisi was awarded man of the match.

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