A Douglas side with an average age of just 20 overcame stiff resistance at Oldershaw to bag a 22-15 win.
First half tries from Niall Killey, Bryn Snellgrove and Conor McCoghan saw Douglas 15-12 in front at half-time.
Snellgrove added another after the break which was converted by Tom Chamberlain and this was enough to seal the game.
Shooting: Winter series gets underway
Ward, Berg and Parr lead the way
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Manxman one of six riders on British Cycling shortlist
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Castletown stay four points clear atop Division 2
Rugby: Vagabonds Ladies stay top with another victory
Vagabonds men and Douglas also take respective wins on home soil