South Africa’s former President Jacob Zuma has unleashed an extraordinary attack on his successor.

In a leaked letter, Mr Zuma said President Cyril Ramaphosa had betrayed the governing ANC and was working in the service of white businesses.

Even for a party consumed by factionalism, this was an explosively vitriolic letter.

Mr Zuma accused his successor of desecrating the graves of "young men and women who lived and died cruel deaths in the hands of apartheid security forces and mercenaries".

He said Mr Ramaphosa was betraying the ANC, to save his own skin.

Worse, he was trying to destroy the party, in order to surrender control to powerful white business interests.

The timing of the letter is significant

Mr Zuma is facing a mountain of corruption allegations, and his long-postponed trial is getting close.

But more imminently, the ANC’s top decision-making body is holding an important meeting this weekend, and the faction linked to Mr Zuma is clearly looking to drum up support.

President Ramaphosa recently lashed out at corruption in the party, describing the ANC as accused number one.

The fury of the backlash against him is no surprise.

More to the point, it suggests that South Africa’s law enforcement agencies may be starting to make some very powerful people, very nervous indeed.