It seems almost impossible now for Deputy President Jacob Zuma to avoid giving evidence in the corruption trial of Durban businessman Schabir Shaik.

A revolving credit agreement signed by Zuma was provisionally entered into evidence this week and the state says it will dispute that it is an authentic document.

The agreement is signed by both Shaik and Zuma, dated 1999 and, according to Shaik's counsel, Francois van Zyl SC, filed at parliament in the confidential register.

For the court to get access to the original document, Zuma will have to waive his privilege.

Both sides now have a significant document, the authenticity of which is disputed by the other. The state has a fax setting out the conditions of a bribe to Zuma, and Shaik has a revolving credit agreement.

The trail of money from Shaik to Zuma is an essential element of the state's case, as it is alleged that through years of "payments" a "general corrupt relationship" was formed between the two men.

This, the state further alleges, eventually culminated in Shaik soliciting a bribe on behalf of Zuma from French arms company Thint. The coming week might see Shaik's legal team wrapping up its cross-examination.

During the cross-examination of Johan van der Walt, the forensic auditor, it emerged that the revolving credit agreement was one of three acknowledgments of debt signed by Zuma. In two of them Shaik charged no interest. In this one he charged interest at prime plus 2 percent.

It further emerged that Zuma might have repaid Shaik more than the state has recognised. But, as ever, Van der Walt, clearly a veteran witness, indicated to the court that to him it is the pattern that counts and not so much the specific pieces.

Shaik, in turn, or so Van Zyl indicated, would say that the payments he made to Zuma were no secret, either to those who worked at Nkobi or to outsiders.

The agreement itself is barely two pages long. On it, Shaik's name is spelt incorrectly. According to Van Zyl, it had been renewed since it lapsed in May this year, but Shaik and Zuma had not got around to signing the new documents.

"I assume you will tell me what the outstanding balances and interest are," Van der Walt said to Van Zyl during cross-examination.

"Never assume anything in a court of law," Van Zyl answered.

The trial continues.

With acknowledgements to Estelle Ellis and the Sunday Independent.

* A classic case of : "f you don't like my principles, I've got others".