In the mid twentieth century, Middle Hill transitioned to use as an aerial farm for the Ministry of Defence.

Middle Hill is in Gibraltar, the British Overseas Territory at the southern end of the Iberian Peninsula.

Approximately 500 Spanish soldiers, led by a goat herder, scaled the Rock of Gibraltar from the south side and made it to St. Michael's Cave, where they stayed the first night.

[6][7] By 1727, Middle Hill Battery had been constructed and a gun had been mounted; the emplacement continued to be used and upgraded for more than two centuries.

However, illegal provisioning resulted in splitting of the Apes' Den population, such that by 2004, there were six groups in the Upper Rock Nature Reserve.

In one case, it refers to the apes who are provisioned at a group of derelict buildings just southeast of Middle Hill Battery.

[8] For decades, Middle Hill was a Ministry of Defence site, where members of the public were excluded and unauthorised entry was considered a criminal offence.

The proposal for Middle Hill included the recommendation that it be named a biological reserve with access to the public only on a prearranged basis.