Alec Tiley scored the game winner 15:30 into overtime and the Waterloo Siskins eged London 3-2 to win the Sutherland Cup.
The Siskins played catch-up all game with London's Cal Davis opening the scoring with a power play goal just over five minutes into the second. Curtis Rawn answered for Waterloo with just six seconds to go in the middle frame.
Davis put the Nationals ahead again just 10 seconds into the third, assisted by James Turner. Sam Spaedt tied the game with an unassisted power play goal with just over four minutes left in regulation.
Matt Onuska made 33 saves for the Siskins. Zachary Springer stopped 33 shots for the Nationals.
