Complex sentence: In 1959-60, the Royal Navy fought hard to retain the "Swiftsure", to a new modernisation pattern as a Cruiser-helicopter carrier, to a design which was largely implemented a decade later on its half-sisters HMS Tiger and HMS Blake.
Split into simpler sentences: In 1959-60, the Royal Navy fought hard to retain the "Swiftsure", to a new modernisation pattern as a Cruiser-helicopter carrier. To to a design which was largely implemented a decade later on its half-sisters HMS Tiger and HMS Blake.