Looking out from King Charles' Castle over the channel which runs between Tresco and Bryher. This area of water is a popular anchorage, and has been for centuries, hence the fortifications.
The tower in the foreground is known as Cromwell's Castle and was built on a more effective site than the existing castle higher on the headland.
The rock islet towards the centre of the photo is known as Hangman's Island. One story is they were the site of some hangings by Admiral Blake in the 17th century, however it is more likely the name is derived from the Cornish for rock - "an men".