President Thabo Mbeki is expected to be called as a witness in the corruption trial of former deputy president Jacob Zuma in the High Court in Durban next year.

It is understood the president has been informed that he is a potential witness, as are a number of other high-ranking ministers, and that he will be asked to testify about a letter sent in January 2001 by Zuma, as leader of government business, to Gavin Woods, then the head of parliament's select committee on public accounts (Scopa).

Zuma, it is understood, claims that although he signed the letter it was actually written by Mbeki, working in tandem with a cluster of ministers who were at the time tasked with "sorting out" the arms deal.

Murphy Morobe, the head of communications in the presidency, said yesterday that he could make no comment about Mbeki being called to court.

If Mbeki testifies it will be the first time a South African head of state has been called to court as a witness in a criminal trial. Early in 1998, former president Nelson Mandela testified in court after South African Rugby Football Union (Sarfu) chief Louis Luyt claimed Mandela had not applied his mind in allowing an investigation of Sarfu. That was, however, a civil matter.

The strong possibility that Mbeki will be called emerged after Friday morning's delivery of the National Prosecuting Authority's (NPA) provisional indictment against Zuma to various legal teams. The former deputy president is charged with two counts of corruption.

Besides the inclusion of similar corruption charges against two local subsidiaries of the French arms company Thales, the indictment is virtually a mirror of the one brought by the NPA against Schabir Shaik, Zuma's former financial adviser who was sentenced to 15 years in jail for corruption and fraud.

One of the main charges against Zuma, as against Shaik, is that he was allegedly party to Shaik arranging a bribe for Zuma from French arms company Thales. The bribe was allegedly for Zuma's protection amid a government investigation into the multibillion-rand arms deal.

One of the pieces of crucial evidence against Shaik in this connection - and against Zuma too, in Friday's indictment - was the letter allegedly written by Zuma to Woods.

Written in January 2001, the letter contained the sentence: "Furthermore we are convinced that there is no need for the Heath Special Investigating Unit to be involved in any investigation of the defence acquisition."

It informed Scopa that further investigation of the arms deal was clearly unnecessary.

In his judgment in Shaik's trial, the letter was said by Judge Hilary Squires to be "hostile", crowing and additional proof that Zuma had been carrying out the task for which he had allegedly been bribed by Shaik and Thales: to protect the Shaik companies, which had won part of one of the tenders in the arms deal, from further scrutiny.

But it is claimed that although Zuma may have signed the letter, the author was Mbeki, working with the cluster of ministers tasked with sorting out the fuss then surrounding the arms deal. It is about this that Zuma's defence team plans to call the president to testify.

At the time of Shaik's trial it was known by a number of people that Zuma claimed not to have composed the letter, but it is understood that - unaware that Squires would place so much emphasis on it - Shaik's defence team opted not to pursue the issue. Zuma's defence is unlikely to make the same decision.

There is also a small - but highly significant - difference in the Zuma indictment to the one brought against Shaik, which is also likely to be picked up by Zuma's defence.

The difference is in connection with the so-called encrypted fax sent by Alain Thetard, then local director of Thales, to his bosses in France. In the fax Thetard is alleged to have set out the terms of Zuma's alleged bribe.

In the Zuma indictment the fax is called a "draft encrypted fax", not "the encrypted fax", as in the indictment against Shaik, and it is referred to as a fax that was "composed" but not necessarily sent.

The new phrasing is thought to reflect the NPA's concern that, although Squires refused Shaik leave to appeal on the first count on which he was convicted ("a general corrupt relationship"), he did allow Shaik leave to appeal on the third count, which dealt with the fax and the alleged bribe to Zuma.

Charged alongside Jacob Gedleyihlekisa Zuma, accused number one, are Thint Holding Pty Ltd (Southern Africa), accused number two, and Thint Pty Ltd, accused number three.

The second accused is owned by Thales and it in turn holds 80 percent of Thint Pty Ltd. Nkobi Holdings, the company owned by Shaik and now managed by his brother, Mo, holds the other 20 percent of Thint Pty Ltd.

Zuma and the two companies are each charged with two counts of corruption.

The main charge against Zuma is that he benefited in a corrupt manner to the tune of about R1,3-million from his relationship with Shaik and was therefore part of a generally corrupt relationship.

It is alleged that Zuma, previously a member of the KwaZulu-Natal legislature and the provincial minister of economic affairs and tourism, then deputy president of South Africa from June 1999, was in a position to recompense Shaik for payment by using his influence in a number of areas.

Appended to the indictment is a list of payouts allegedly made to Zuma by Shaik. They total R1 269 224,91. Some of it is alleged to have gone towards the construction of Zuma's home at Nkandla, the cost of which, according to the state, was R1 340 000.

Zuma is also alleged to have known about and to have co-operated in arrangements made by Shaik with Thales for Zuma to be paid R500 000 a year for two years in return for his "protection" from arms deal investigations as well as further assistance.

The Nkobi-Thales consortium had won a tender for the supply of combat suites in the naval corvettes ordered as part of the Strategic Defence Package Acquisition Programme (the arms deal). The tender was worth R450-million to Shaik and Thales. The total corvette deal was worth R1,3-billion.

Both Thint companies are charged with having been party to the arms deal bribe request.

Neither Thint nor Thetard was charged during Shaik's trial because Penuell Maduna, the then minister of justice, and Bulelani Ngcuka, the former Scorpions chief, offered Thint immunity from prosecution in return for an affidavit from Thetard about the fax.

As it turned out, Thetard testified that the fax was not a "bribe document" but merely his doodlings during a meeting. However, it is understood that Ngcuka wanted proof, for the Shaik trial, that the fax document was not simply a fabrication that was effectively provided by Thetard's affidavit.

Sources at Thales in France have said immunity was granted to them previously, therefore the company would not co-operate in any new matter. Pierre Moynot, the local Thint director, is out of the country but said last week "the matter" had not happened on his watch, so there was little for him to say.

Zuma will appear on Saturday in the Durban regional court for his case to be referred to the high court on July 31 next year.

With acknowledgements to Jeremy Gordin and the Sunday Independent.