Britain needed separate available flight decks for fixed-wing strike and for the helicopters supporting an amphibious assault. The four ballistic-missile submarines used to keep one deterrent boat continuously at sea provide the comparison, accounting for deep maintenance, short maintenance, training, and patrol cycles. Five flight decks would provide a contingency hull and make two ships available at short notice with replacements behind them. Building three Invincible-class carriers and later HMS Ocean left a thinner margin than the operational requirement justified.
Notable Point · 1:01:02-1:02:49
From four deterrent submarines to five usable flight decks
The four-boat deterrent model explains why sustaining two different flight-deck roles would require more than three carriers and an improvised amphibious ship.