Keeping small-boat designs alive after the war

When did the Royal Navy stop operating motor torpedo boats and motor gunboats?

The last operational boats appear to have served into the late 1950s, while experimental designs continued into the 1960s to preserve mobilization options.

Royal Navy MTBs or MGBs appear to have remained active into roughly the late 1950s, with experimental designs continuing into the 1960s. Retaining a small development stream made sense in peacetime. Building successive improved boats preserved design knowledge without committing the fleet to mass production of a type that might soon be obsolete. If war came, the navy could place a large order for the latest tested design instead of restarting the entire learning process. Modest peacetime procurement preserved the option of rapid wartime expansion.