Dele Alli had twice hit the woodwork earlier in the game before Son fired home with 10 minutes to go to earn north London bragging rights once again.
Talk over Harry Kane’s future continues to dominate in north London, but Son proved Spurs will still have a world-class finisher in their ranks even if his team-mate departs.
Arsenal continue to struggle in attack themselves, with Pierre-Emerick Aubameyang barely having a sniff and Nicolas Pepe’s decision-making struggles once again on show.
Alexandre Lacazette hit the woodwork in the first half, which was the nearest the Gunners came. A worrying trend for Mikel Arteta with his team appearing out of ideas as they approach the opposition penalty area.
With their Premier League opener against Brentford just five days away, Arteta is expected to stick with the same team but will need a much-improved showing.