This former pill box is at the end of Bond's Mill Bridge. This is an octagonal two-storey pill box constructed of brick and concrete during World War II, and was likely to have had an anti-aircraft gun on the roof. This was to protect an adjacent aircraft instrument factory, and was also part of 'Stop Line Green' (for more information on Stop Line Green see Stonepitts pill box link in the right panel). The large modern windows would have been put in after the war.
This structure is also known as Bond's Mill Gatehouse.
More recently the building has been used as a CCT Visitor Centre. Note, there are no facilities here due to its small size.
(Tap / click images to enlarge)