On 29 April 2023, a Boeing 737-800 night takeoff clearance at Sydney was delayed by unexpectedly slow landing traffic clearance and it became necessary for another Boeing 737-800 on approach to the same runway to be instructed to go around and minimum separation was reduced below safe distances both laterally and vertically. It was found that the conflict had resulted from a combination of inappropriate intervention by the Tower Supervisor and the controller’s own actions. A review of potential conflicts during mixed mode runway use at Sydney to improve resilience to inevitable pilot and controller error was initiated by ATC.