Ronnie Kasrils was Minister of the Intelligence Services of South Africa from 2004 to 2008.

It is scarcely surprising in South Africa, where conspiracy theories thrive, that the parole of Janusz Waluś, the assassin of South African Communist Party General Secretary, Chris Hani, should revive questions about the April 1993 murder.

It is understandable that Chris Hani's family, and the party he led, should have been the first to question whether a wider conspiracy existed.

Conspiracies abound, but for matters of such national importance, it is vital to do sober research, investigation and analysis. Those who thrust themselves to the fore with speculative, fanciful and libellous storytelling, should at least warrant circumspection. They invariably excite the most basic of prejudices, and far from clarifying possible leads, muddy the waters. RW Johnson's latest foray on the business news site, BizNews, is one such aberration.

Johnson's article is a rehash of the theory peddled in his book, South Africa's Brave New World, published in 2009, correctly described by a Guardian reviewer at the time as "a record of pretty well every piece of unsubstantiated gossip to have circulated South Africa's rumour mills".

Johnson is no stranger to controversy, having outraged the likes...