The castles at Pendennis and St Mawes were built to protect the Carrick Roads and Falmouth in Cornwall. Both appear to have been completed by 1543. They formed part of a wider network of coastal castles, including Deal and Walmer, and the Solent. For further details of the programme of defence see here.
Both castles were placed in State Guardianship in 1920 (from the War Office), and they were requisitioned for military purposes in the Second World War. They were re-opened to the public in 1946.
A souvenir guide was produced in 1963, was continued into the 1970s under the Department of the Environment. This provides a guide to both castles as well as a historical introduction.
English Heritage produced a colour guide to both castles in 1999 by Richard Linzey. It includes tours of both castles, as well as a page on the National Trust property of St Anthony Head Battery.
The latest guide by Paul Pattison has extended tours of both castles. There are special topics that include smuggling and piracy, the submarine minefield, as well as St Anthony Head. Foldout plans are printed inside the cover.