The imprisonment for defrauding parliament of former ANC parliamentary chief whip Tony Yengeni raises profound political, moral and even philosophical issues for post-apartheid South Africa.

Since the primary cause of Yengeni's crime was banal greed, he may be seen as a metaphor for the loss of South Africa's innocence after the heady days of the release of Nelson Mandela and the birth of a brave new world.

Now a man in his early 50s, Yengeni is one of the generation of young black men and women who, armed with a vision of establishing a just and egalitarian society, emerged in the turbulent 1970s to challenge the oppressive white-dominated racial oligarchy. But many of that generation have abandoned their idealism for a compulsive desire to accumulate riches and possessions.

The stages of Yengeni's metamorphosis from political activist to guerrilla commander to chastised prisoner include:

His political baptism as a cadre of the black consciousness movement, and subsequent ideological shift to the ANC and recruitment into its army, Umkhonto weSizwe.

His return to Western Cape as a guerrilla commander and his capture and torture by the security police.

His rise in the ANC in the Western Cape in the 1990s, his election to parliament as an ANC member and his appointment as ANC chief whip.

His acceptance of a discount of nearly R170 000 on the purchase of a limousine from European Aeronautic Defence and Space (EADS), even though he was the chairperson of the joint parliamentary defence committee and the company was a bidder for a contract to sell expensive modern weapons to South Africa.

From then on nemesis begins to overtake him. It starts with the investigation by the Scorpions into his purchase of the vehicle and leads, inexorably, to his conviction for fraud in the Pretoria regional court, where he was sentenced to four years imprisonment. Then there is his prolonged but ultimately unsuccessful attempt to have the conviction and sentence overturned.

Terry Crawford-Browne, the chairperson of the South African chapter of Economists Allied for Arms Reduction, describes the period between Yengeni's purchase of the vehicle at a heavily discounted price in 1998 and his imprisonment on August 24 2006 as "eight years of lies, evasions and cover-ups".

Some of Yengeni's adversaries in parliament seem to have given vent to unrestrained delight when it became clear that he could not avoid incarceration, perhaps because they concentrated on his self-justifying mendacity as a politician to the exclusion of his fortitude as ANC combatant, prisoner and torture victim.

His comrades in the ANC, including the Western Cape premier, Ebrahim Rasool, and the present ANC chief whip, Mbulelo Goniwe, appear to have gone too far in the opposite direction. By escorting Yengeni to Pollsmoor Prison when he handed himself over to the authorities they seem to be signalling that they condone his crime and disapprove of the judicial decision to imprison him.

Yengeni will retain his position on the ANC national executive committee unless the ANC disciplinary committee decides to deprive him of it. The minister in the presidency, Essop Pahad, who describes Yengeni as "a very old friend", is not aware of any decision to unseat him.

Yengeni has left a remark for us to contemplate pending his expected release on parole in eight months. His supporters will interpret it as a typically feisty departing shot, but his opponents will construe it as a predictably arrogant valedictory statement. Yengeni's boast still rings in the ears: "Those who think that prison is going to break me are in for a rude shock".

Yengeni insists that he was unfairly tried for a matter - failing to declare the discount to parliament - that parliament should have adjudicated and settled. As he puts it, a parliamentary issue was "hijacked and criminalised" (omitting to explain that he had entered into a plea bargain with the prosecution to admit to defrauding parliament rather than face the more serious charge of corruption).

Yengeni's presentation of his offence as a mere parliamentary infringement is almost certain to be fiercely debated in political circles.

What is critical is whether Yengeni accepted the discount as a quid pro quo for using his influence as chairperson of the parliamentary defence committee to advance the chances of EADS winning a tender to supply arms to South Africa.

Assuming that Yengeni did enter into such an agreement, could the state have proved it in court?

A common theme in the Yengeni case and in the trial on corruption charges of former deputy president Jacob Zuma is the leaking of details of the investigations to select news media. It is improbable that this is coincidental.

A report in Noseweek in August 2000 that millions of rands flowed into the account of former defence minister Joe Modise from Germany shortly after he resigned in June 1999 is not irrelevant, especially as the money transfer occurred as Modise emerged as the chairperson and major shareholder of Conlog, a company with interests in the armaments industry.

The sequel to the publication of Noseweek's story about Modise is worth recording.

Noseweek received a letter from Modise's lawyers repudiating the report, threatening to institute legal proceedings for damages and pressing for an "appropriate apology and retraction".

Noseweek refused to publish the apology and retraction unless it was informed which South African bankers had, as the lawyers claimed, arranged for the money to be "loaned" to Modise, and what the repayment arrangements were. The lawyers chose not to pursue the matter.

One wonders why.

Patrick Laurence is the editor of Focus, a journal of the Helen Suzman Foundation. He writes in his personal capacity

With acknowledgements to Patrick Laurence and The Sunday Independent.