The correct answer to the question is option 2: William Dalrymple. In his book "The Last Mughal - The Fall of a Dynasty, Delhi 1857," Dalrymple examines the final days of the Mughal Empire in India. The book primarily focuses on the events leading up to and during the Indian Rebellion of 1857, also known as the Sepoy Mutiny.

Option 1: John Kirkland - This is not the correct answer. There is no known association of John Kirkland with the book "The Last Mughal."

Option 3: Thomas Wilson - This is not the correct answer. There is no known association of Thomas Wilson with the book "The Last Mughal."

Option 4: Simon Digby - This is not the correct answer. There is no known association of Simon Digby with the book "The Last Mughal."

Therefore, the answer remains option 2: William Dalrymple.