Small derelict brick building

There is a small blue plaque which notes the role of the former swing bridge but does not describe what this small building was for. My guess is that it housed the controls for the swing bridge, or perhaps it was something else to do with the Hayle Wharves Branch Line (which was what used to be carried over the swing bridge). Suitable for the Derelict challenge, thank-you Marlieske for hosting.