Its dying because you are only watering every 2 weeks. Even in London, that's not enough. Do a scratch test on the trunk to see if its alive. (scratch the bark with something sharp. If the tissue just under the bark is green, the tree is alive. If its brown or hard, the tree is dead) If you see green, fill the bucket its in with water and let the whole pot soak for 30 minutes to make sure the water has penetrated all the way to the middle of the root ball.
From the broken spot in the pot, it looks quite root bound. It needs to be planted in a bigger pot or in the ground but, its not the time to tackle that task.