Built by a grieving widow in a commanding position in a bluebell wood on Shooters Hill, this wonderfully Gothic 18th-century tower was designed by architect Richard Jupp in an unusual triangular shape. It also has an impressive viewing platform.
The widow was Anne, Lady James, whose husband Sir William died in 1783, and the castle commemorates her love for her husband and his greatest adventure: destroying a band of pirates in 1755 in their fortress - Severn Droog - off the west coast of Malabar.
The castle is both Grade II* listed and on English Heritage's Buildings at Risk register, and the motivated volunteers who'll show you round ensure all your entry fee goes towards ongoing preservation work.
The tea room is open Wed-Sun in season (www.castlewoodtearoom.co.uk).