Player castle placed at 4:23​ CPU surrenders at 20:21​ Total Time 15:58​

Played on an emulated A1200

I used a strategy of giving the CPU a head start before placing the player castle. The idea being to complete the first player guard hut at around the same time the CPU builds its first guards hut. Once the CPU has built its guard huts and 1 soldier has occupied it place the CPU castle under siege to prevent reinforcements and attack the guard huts.

This seems to trigger the CPU into an early surrender.