The Leander-class, or Type 12I (Improved) frigates, comprising twenty-six vessels, was among the most numerous and long-lived classes of frigate in the Royal Navy's modern history. The class was built in three batches between 1959 and 1973. It had an unusually high public profile, due to the popular BBC television drama series Warship. The Leander silhouette became synonymous with the Royal Navy through the 1960s until the 1980s.

Warship is a British television drama series produced by the BBC and broadcast between 1973 and 1977. The series was set contemporaneously and depicted life on board the fictitious Royal Navy frigate HMS Hero. Four series were produced with 45 episodes made in total.