Gatwa, who surprisingly left the BBC sci-fi series after just two seasons, described the job as incredibly stimulating but also "very exhausting".
He previously stated on Sunday with Laura Kuenssberg that he left due to being "tired" and the role being physically, emotionally, and mentally "strenuous".
Despite the toll, Gatwa expressed deep gratitude for the "gift of a job" and the passionate Doctor Who fanbase.
Gatwa is currently promoting his new West End play, Born With Teeth, where he plays Christopher Marlowe, and also commented on his withdrawal from Eurovision due to a busy schedule.