Izale McLeod's hat-trick gave Barnet's survival hopes a huge boost as Gillingham's 16-game unbeaten run came to a crashing halt with a 4-2 defeat.
After Andy Barcham had cancelled out Mark Byrne's opener, the home defence crumbled as McLeod pounced in first-half injury time before bagging two after the break.
Barnet took a shock lead on 13 minutes as Mark Marshall's cross wasn't dealt with allowing Byrne to pounce but the Gills equaliser arrived soon after when Sam Walker kept out Cody McDonald's effort only for Barcham to poke home the rebound from four yards.
Luke Rooney then hit the post for the hosts but they were hit with a sucker punch when Jude Stirling headed Marshall's cross back across goal for McLeod to head in.
Things got worse for Andy Hessenthaler's men seven minutes into the second half as McLeod found space in the area to lash in the Bees' third.
His fourth came from the penalty spot after Matt Lawrence's foul on Byrne and, even though he missed a second spotkick and Barcham bagged a second, the travelling Bees fans celebrated a tremendous victory.
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