Definately some sort of base to keep all the UFO's that crashed eh?

With all due respect but National Service (2 tears compulsory for all white SA males above 18 years) stopped been compulsory from 1992. How credible is the rest of your story?

In 1980, Special Forces Headquarters was moved to Swartkop Park nature reserve outside Pretoria, which has subsequently unofficially been called “Speskop” within the Special Forces community.

As for "Silvermine" there is nothing glamorous there. No 12 floors down. It was an early (single level) bunker overlooking the bay, built years ago when SA was still a Union, (Pre 1960's, pre-"communist threat". Nothing secretive.

On 8 July 1981 Lieutenant Adriano Bomba flew a MiG 17 from Maputo to over the Kruger Park, to South Africa, after which he was intercepted and escorted to land at Air Force Base Hoedspruit. On landing he asked for political asylum. The aircraft was later returned to Maputo by road, after extensive examination, flight testing and an appearance at an air show. [in 1982 he went back to Mozambique and joined the Mozabique National Resistance to fight FRELIMO - Lt Bomba, who had been granted permanent residence in South Af-rica, had been employed in a civilian capacity as he had no furtheri nterest in flying]

No underground bases there.