In the winter of 2000, the National Prosecuting Authority's investigation into Deputy President Jacob Zuma and his business associate Schabir Shaik was hanging by a thread.

It was saved by unexpected international co-operation on the high stage and a simultaneous, crucial, low-key, coffee-shop meeting .

Testimony in the Shaik corruption trial this week has demonstrated how close the investigation came to reaching an awkward impasse and the critical role that skilled and determined investigators played in rescuing it.

The person responsible for maintaining the pressure, Scorpions prosecutor Gerda Ferreira, provided new insights this week about how the investigation unfolded, including the trouble she had convincing whistleblower Susan Delique to participate .

By the winter of 2000 , the investigating team had at best a circumstantial case. They knew from Arthur Andersen accountants Gary Parker and David Read that an employee of French arms company Thomson CSF (now Thales) had reported what seemed to be an attempt at bribery.

Ironically, the accounting firm collapsed when Parker and Read's colleagues in the US declined to follow the moral example of their counterparts and the Enron scandal ensued.

The investigators now knew that, tantalisingly, a document existed that tied Zuma and Shaik to an alleged attempt to solicit a bribe from Thomson CSF.

But they did not have the document, and neither could they explain the chain of events that led to its existence, let alone produce in court the witnesses that would testify to the circumstances and verify the documents.

The result was a stuttering attempt to get Delique to produce the documents. Ferreira testified this week that the first time she spoke to Delique, the Thomson CSF employee slammed the phone down on her. Delique worked for a very short time for Alain Thetard, who was for a time Thomson CSF's head of operations.

However, Delique was obviously conscience-stricken, because she phoned Ferreira back the same day, confirming that she did have the document. She discovered a written copy of the encrypted fax on a computer disk at her home.

The document in question was what subsequently became known as the "encrypted fax", which names both Zuma and Shaik.

Ferreira said this week that Delique would only hand the document over in exchange for a written undertaking that she would never have to testify about it in court. She would not even meet the Scorpions, and offered only to deliver the document to the Scorpions' offices.

Delique then apparently had another change of heart, or at least a change of approach. She did meet Ferreira alone at her insistence at a coffee shop in Kyalami.

For Ferreira, the news was both good and bad. Delique told Ferreira a good deal of background information on the company including the fact that certain critical Thomson CSF documents were kept hidden in the ceiling.

But the crucial fax was lost, apparently mislaid in a shopping trolley in a supermarket, Delique told Ferreira. Happily for the investigators, the winter turned to spring. The handwritten version of the fax was later found after Delique was fired from the company.

And last year, Delique even submitted to the ordeal of giving evidence at the Durban trial.

On the same day Delique met Ferreira in October 2000, searches had taken place at Thomson CSF offices in Paris, Mauritius and SA .

The searches provided plenty of documentation, but the critical fax was not found in Paris or Mauritius.

It was discovered because a level of trust had developed between an investigator and a critical witness at a coffee shop in Kyalami.

With acknowledgements to Tim Cohen and Business Day.