Former Glasgow Tigers racer Aaron Summers (pictured), now with Berwick Bandits, came back to haunt his former paymasters.
The Australian, guesting for Newcastle Diamonds, powered to a key win in the third last heat and was followed home by team-mate Ben Barker.
That put the Tyneside team 41-37 ahead and a 4-2 in the next race helped secure a welcome 48-42 win for the English side.
Glasgow remain top of the 12-strong table but only have a slender lead over second-placed Edinburgh Monarchs.
Another former Glasgow racer, Adam Roynon, top scored for Diamonds with 14 points with Max Clegg next best on 11 points.
Guest Steve Worrall was best for Tigers with ten points.