The "Implacable" class had its origin as an improved version of the "Illustrious"-class aircraft carriers for the 1938 Naval Programme. They were designed to be faster, and to carry an additional dozen aircraft at the expense of reduced armour protection to remain within the available from the tonnage allowed by the Washington Naval Treaty. "Implacable" was long overall and at the waterline. Her beam was at the waterline and she had a draught of at deep load. The "Implacable"-class ships were significantly overweight and displaced at deep load. The ships had metacentric heights of at light load and at deep load as completed. "Implacable"s complement was approximately 2,300 officers and enlisted men in 1945.