It was not included in the original list of defensive structures proposed by the Royal Commission on the Defence of the United Kingdom in 1860 .
It was not was conceived later and implemented as an experimental redoubt as opposed to a more substantial fort .
It was not included in the original list of defensive structures proposed by the Royal Commission on the Defence of the United Kingdom in 1860 , but was conceived later and implemented as an experimental redoubt as opposed to a more substantial fort .