This? Margaret Thatcher gave the SA government 7 nukes and this was a test of one of them on a barge, the other was at McQuarie Island but it did not explode. When SA became democratic these nukes were sold off on the international market, mostly to NK and islamic forces.

There is a rumour going around that one of these nukes was intercepted in a warehouse close to London during the Olmypic Games... I have no source for this as the website is no more.