British second rates answered the threat of Spanish three-deckers

The 112-gun Príncipe de Asturias, of the Santa Ana class, was the youngest first rate at Trafalgar. Britain had newer first rates elsewhere, but its recently built second rates were present at the battle. A second rate cost less than a first rate while still giving the Royal Navy a third gun deck. That height mattered against large Spanish ships, which could fire down onto two-deck opponents and gain an advantage in boarding or close action. Other navies tended to favor third rates for numbers or first rates for the greatest individual fighting power. British second rates filled the space between those choices.