Write down the opening description of Jack.

From the text:

The boy who controlled them was dressed in the same way though his cap badge was golden.When his party was about ten yards from the platform he shouted an order and they halted, gasping, sweating, swaying in the fierce light. The boy himself came forward, vaulted on to the platform with his cloak flying, and peered into what to him was almost complete darkness.

From Jack's description, we can infer that he is charismatic, confident, and that he might have leadership abilities.