Due to its location Signal Hill has always been the perfect place from which to warn the Castle agains possible approaching enemy fleets. In 1673, when Isbrand Goske became Governor of the Cape, it was decided that three men would keep watch on the Lion’s Head, with one or two little guns. By the late 1700s’ the signalman would hoist a flag once a ship was spotted, and would fire a gunshot per ship. With the establishment of a regular mail service between England and the Cape in 1815, and increased trade, signalling operations became arduous.
It was decided in 1833 to provide ships in Table Bay with a time signal by which to set their chronometers and firing a brass bell-mouthed pistol did this. At night the flash from the Observatory roof was watched through telescopes from ships several kilometres away. For some years a time signal was fired from the Imhoff Battery in front of the Cape Town Castle. In 1855 it was decided that the time ball at the south front of the Observatory was not visible from the whole of the Table Bay anchorage, so another one was established at the Lion’s Rump Signal Station. The custom of firing it at noon started in 1903, the year in which Standard Time was introduced in South Africa. A gun at the Imhoff Battery (demolished to build the railway line outside the Castle) that used to signal 1 pm, was then moved to Signal Hill, and was electronically detonated by a charge set off from the Observatory at 12 noon. The gun is not fired on Sundays and public holidays.