The British Empire's naval history is full of tories of success, often against great odds through effective leadership, preparation, abilities, training, luck and available/competitive kit.
But sometimes things do not go well. Ships, the navy and sometimes the empire itself are put into danger through poor leadership. Here are a few of the captains I can think of that through their actions showed they'd be better suited for other tasks than commanding HM ships.
Feel free to suggest others.