Captain Hobbes serves as the commanding officer of the HMS Leviathan, the massive bio-engineered airship that gives the series its name. His appearance in the anime is characterized by dark black hair and a prominent mustache, a design that adapts his literary counterpart for the screen. As the captain of a British military vessel during an alternate version of World War I, Hobbes embodies the archetype of a traditional British officer. He is effective in his command and generally adheres to regulations and protocol, a trait that at times leads other characters, such as the scientist Dr. Nora Barlow, to express frustration with what they perceive as his inflexibility. His name itself is a likely reference to the philosopher Thomas Hobbes, who wrote a famous political treatise titled Leviathan, a connection that adds a layer of intellectual weight to his role as the master of the colossal airship.

In terms of personality, Captain Hobbes is presented as a competent and authoritative figure who runs a tight ship. He is not prone to outbursts or grand gestures but instead demonstrates a steady, rule-bound approach to leadership. While he is suspicious of Prince Alek and his companions for much of the series, this suspicion stems from a practical understanding of military and political realities rather than personal malice. He does not discover the true identity of Deryn Sharp, a young woman disguised as a boy named Dylan to serve in the British Air Service. Instead, he views Dylan as a capable and promising soldier, even personally awarding a medal for service and assigning tasks of significant importance.

Captain Hobbes's primary motivation is the successful operation of the Leviathan and the fulfillment of his duties to the British crown. His decisions are consistently guided by the pressures of the war and the need to protect his ship and crew. He is not driven by personal ambition or a hidden agenda but by a clear sense of military obligation. In the story, he acts as the ultimate authority aboard the airship, setting its course and making critical decisions that affect the protagonists. He formally announces the declaration of war to the crew, negotiates a truce with Count Volger to allow the Leviathan to be repaired, and orders the jettison of weight to avoid a confrontation with an enemy walker. He is the one who officially detains Alek and Volger once Britain and Austria-Hungary are at war, and he later reassigns Deryn to janitorial duties after her true gender is revealed.

His key relationships are defined by his position of command. He has a professional, largely positive relationship with Deryn, valuing her as a soldier without ever piercing her disguise. His relationship with Alek is more tense and fraught with suspicion, as Hobbes is aware that the young prince is a fugitive and a potential liability. However, he never becomes a true antagonist, instead acting as a representative of the system that both protects and restricts the main characters. He works alongside Dr. Barlow, though their interactions are marked by her impatience with his rigid thinking. He also commands other crew members like Mr. Rigby, Mr. Hirst, and Newkirk, relying on them to carry out his orders.

While Captain Hobbes does not undergo a dramatic personal transformation, his development is subtle and reflects the changing circumstances of the war. He grows from being purely suspicious of Alek to eventually approving a medal for the prince’s bravery during a hurricane, showing a capacity to acknowledge actions that earn his respect. His perspective shifts from seeing Alek as a political problem to recognizing his value as a person. In a pivotal moment, he is surprised to learn that Alek is the Prince of Austria, revealing that he was not fully aware of the gravity of the secret being kept on his own ship.

Captain Hobbes does not possess any fantastical or superhuman abilities, as the world of Leviathan distinguishes between Darwinists, who engineer life, and Clankers, who build machines. Instead, his abilities are those of a seasoned naval officer. He is a skilled strategist and a decisive leader capable of managing a complex airship and its diverse crew during wartime. He effectively coordinates missions, such as the plan to use the Behemoth to destroy the enemy ship Goeben, and makes tactical assessments, like when he deems it impossible to target a specific tower on the Goliath due to electromagnetic interference. His authority and command presence are his most significant tools, allowing him to maintain order and pursue his objectives throughout the series.