Who was the Commissioner of Lucknow when the rebels besieged it during the Revolt of 1857?

The correct answer is Henry Lawrence.

Historical Context:
During the Revolt of 1857 (also known as the Indian Rebellion of 1857 or the Sepoy Mutiny), Lucknow was one of the key centers of the uprising. Sir Henry Lawrence was appointed as the Chief Commissioner of the newly annexed province of Awadh (Oudh) in March 1857, with Lucknow serving as its capital.

The Siege of Lucknow:
When the rebellion reached Lucknow in May 1857, Sir Henry Lawrence recognized the gravity of the situation and fortified the British Residency compound, gathering food, ammunition, and reinforcing the defenses. The rebel forces besieged the Residency starting in late June 1857. Henry Lawrence personally directed the defense but was fatally wounded by a shell fragment on July 2, 1857, and passed away two days later. His foresight in stockpiling supplies and fortifying the Residency, however, enabled the garrison to hold out until reinforcements arrived.