Who is Thomas Crean, second officer from Endurance: Shackleton's Incredible Voyage and what is their importance?

Thomas Crean is the second officer of the expedition. He joins the Royal Navy at a young age and by the time of the expedition has undertaken two previous polar expeditions under the direction of Robert Scott, where Crean serves with distinction. Crean likewise serves with distinction during the expedition and is trusted and particularly valued by Shackleton. Crean's even-handed leadership and unflagging optimism earn him the respect of the men and he is generally well-liked.