St Helens
The closest Royal Commission sea fort to the island is St Helens Fort, named after St Helens. Historic England has St Helens Fort listed as a Scheduled Monument https://historicengland.org.uk/listing/the-list/list-entry/1017370/and Grade II Listed Building https://britishlistedbuildings.co.uk/101034399-st-helens-fort-st-helens#.W8yGtPZFyM8 which shows how important it is to the national heritage.