St Brelade dealt local rivals Jersey Wanderers' Premiership title hopes a huge blow as they came away with a 2-1 win from the Hockey Club.
First half-goals from Kyle Hampshire and Dan Romeril secured the win, although Jamie Mourant's stoppage-time free-kick set up a nervous finish.
Wanderers dropped to third after St Paul's crushed St Lawrence 7-1.
Island players Luke Watson and Craig Russell each scored twice as St Paul's went five points clear in second place.
The loss for St Lawrence, coupled with a first win of the season for St Peter, sees them drop into the relegation zone.
St Peter went a point above St Lawrence after a 2-1 home win over Grouville, while St Ouen stay bottom and without a point after suffering a 2-0 loss at Rozel Rovers.
In the Championship leaders Trinity were run close by bottom side Magpies as Daryl Wilson's goal with his club's first attack of the match proved to be the difference between top and bottom.
Trinity are now eight points ahead after the clash between second-placed First Tower and third-placed St Clement was postponed.
Sporting Academics stay fourth after an impressive 6-1 win over St Martin, who are now second-from bottom after Beeches went above them on goal difference thanks to a 3-0 win over Portuguese.