On the whole, the public celebrations that accompany elderly politicians' birthdays are not voluntary. If they are still in power it is not by popular choice and if they are retired their anniversaries are private affairs. Nelson Mandela must surely be the first public figure whose 90th birthday on 18 July 2008 was anticipated with an internationally televised rock concert held in a packed public space in London. The audience on 27 June included a fair share of people who were on average a decade or two older than the crowd that would camp out at Glastonbury the upcoming weekend, but among the statesmen, divas and television personalities there were plenty of fresh faces. It's a fair bet that many of the concert-goers in Hyde Park that day were still learning to stand when Nelson Mandela walked out of his prison cell. For them, the anti-apartheid struggle is a history lesson, something that happened in another country in another time. But the affection and admiration Mandela commands across such a vast and varied public following was very evident. How can we explain it?

Tom Lodge is professor of peace and conflict studies at the University of Limerick, Ireland. He was formerly professor of political studies at the University of the Witwatersrand, South Africa. He is the author of Mandela: A Critical Life (Oxford University Press, 2006). His previous books include Politics in South Africa: From Mandela to Mbeki (Indiana University Press, 2003)

The straightforward answer was the one that Stephen Fry supplied in his interview backstage in Hyde Park. Mandela is a good and great man; such people are rare; and they have an unusual capacity to inspire public optimism and social solidarity. This is all true but it can be only part of the explanation. It doesn't take much imagination to think of public figures with equivalent moral qualities that do not evoke such adulation. Vaclav Havel? Aung San Suu Kyi? It takes a bit more effort to identify public figures with comparably heroic careers, but they exist and indeed include many of Mandela's own compatriots.

The flaws on the icon

It won't be long before the first fully revisionist biographies of Mandela appear and they will emphasise his political shortcomings and moral lapses. Political critics are likely to focus on his early relationship with the South African Communist Party - which at least one influential authority, RW Johnson, thinks he actually joined - as well as (for example) the tactical and strategic errors that he made as the first commander of the African National Congress (ANC's) armed wing, Umkhonto we Sizwe, and his disregard for the most elementary considerations of security.

Those with shorter historical memories might focus on the inconsistencies in Mandela's foreign policy, an area of government in which he assumed a decisive role, promoting a human-rights programme in Africa while be-medalling the Indonesian dictator Suharto for his donations to the ANC. It was Suharto, incidently, who gave Mandela the first of the comfortable tunic-like shirts that are now the distinctive attribute of the "Madiba" sartorial style.

Revisionist critics will also make mileage from Mandela's private life. Mandela's marriage to Winnie was such an important romantic ingredient of his international appeal. Winnie Mandela's own autobiographical writings, Part of My Soul (1985), preceded Mandela's Long Walk to Freedom (1994) as a global bestseller. Yet Mandela's loyalty to Winnie represented (as Elleke Boehmer notes in her superb Nelson Mandela: A Very Short Introduction) "a major moral blind spot"; and it was a blindness with significant public consequences, given his insistence on appointing her to important positions within his party and government which she all too predictably abused.

Also in openDemocracy

Gillian Slovo, "Making history: South Africa's Truth and Reconciliation Commission" (5 December 2002)

John Matshikiza, "Johannesburg: shanty city, instant city" (13 December 2002)

Paul Kingsnorth, "Apartheid: the sequel" (20 May 2003)

Nahla Valji, "South Africa: no justice without reparation" (2 July 2003)

Achille Mbembe, "South Africa's second coming: the Nongqawuse syndrome" (15 June 2006)

Achille Mbembe, "Whiteness without apartheid: the limits of racial freedom" (4 July 2007)Roger Southall, "South African lessons for Kenya" (8 January 2008)

Roger Southall, "South Africa and Zimbabwe: the end of ‘quiet diplomacy'?" (29 April 2008)

Faten Aggad & Elizabeth Sidiropoulos, "South Africa's tipping-point" (2 June 2008) on South African politics and society:

All the issues here have already been well worked over even by the "authorised" biographers. What receives less attention is the marriage itself. It was Mandela's second marriage. Mandela's behaviour in his first marriage was unattractive by any standard. On one occasion his wife Evelyn arrived back home to discover a mistress installed in the bedroom. Mandela was faithful and loyal - to a fault, as already noted - to Winnie. In the context of the time, he was a considerate husband, teaching her to drive and arranging an ante-nuptial contract. All too often, though, if we are to believe Winnie, she found herself cut off from him, excluded from the first passions in his life. When Mandela went "underground" in March 1961 he bid her only the most impersonal of farewells: one story has it that he stayed in the car outside while one of his political minders entered the house to ask Winnie to pack a suitcase.

My guess is that Mandela's reputation will survive revisionist deconstructions. He himself has made no secret of his personal and public failures; and it is indeed the confessional quality of his autobiographical testimony, both published and unpublished, that makes him such an attractively accessible public hero. Very few public personalities have had so much of their intimate correspondence published during their active careers, and Mandela's private voice is compelling because of its vulnerability, and its self-insight. Mandela knew he had failed his children and imposed privations on his wife at a time when she could not be an equal partner in his decisions. Through the years in prison he became more uncomfortably conscious of his increasing age and of her relative youth, of his powerlessness to help her, and of her increasing potency - a consciousness that could prompt him to defend the inexcusable, as in, for example, his approval of her notorious speech about "necklacing".

Mandela's iconography projects an ordinary man with ordinary weaknesses who was nevertheless capable of magnificent courage, compassionate generosity, and at certain key points, righteous acts. Identifying mistakes and blemishes hardly detracts from these noble capacities and actions - it only makes them more remarkable.

The politics of style

Another revisionist interpretive approach is to understand Mandela's greatness as a collectively manufactured achievement - the deliberate assembly of a messianic personality originating in a movement's awareness of its own organisational shortcomings and willingness to compensate for them by directing its ideas through a charismatic individual. This is indeed part of Mandela's story, for the ANC certainly began to intentionally contrive a public legend around Mandela's leadership well before he went to prison - during the 1952 "defiance campaign", when collective decisions and activities were attributed to his personal genius. The appearance in South Africa at this time of popular photo-journalism aimed at black readers made this easier, and Mandela himself took pains to ensure that the media images matched the messages he and his comrades wished to project.

How much of Mandela's "voice" represents his own testimony and how much is the outcome of a collectively created script will remain a point of biographical contention. For example, Mandela's autobiography was ghosted but much of it sticks quite closely to a manuscript Mandela composed in prison that never appeared in print. So how much of Long Walk to Freedom (published in a new edition in 2002 as No Easy Walk to Freedom) expresses Mandela's own understanding of his past? Mandela certainly didn't write all his speeches; but was his most powerful public address, his statement from the dock at the "Rivonia" trial of 1963-64, his own work? All the textual evidence indicates that he wrote it, but detractors have ascribed authorship to defence lawyers as well as senior figures in the Communist Party.

The internationalisation of Mandela's appeal can be explained by the circumstances that enabled "Anti-Apartheid" to become a global cause: decolonisation and the creation of the "third world", the expansion of European higher education that generated such a massive activist constituency for new "post-industrial" social movements, the empowerment of African Americans, the transnational revival of liberal democracy at the end of the cold war, among other factors. Mandela's political achievements were magnified by the extent to which South African politics has attracted international empathy, partly a consequence of the representation of that politics as moral fable in a globally influential English-language literary genre. In another words, as a public personality, Mandela is a cosmopolitan social construction, a celebrity in a global setting in which media personalities have become generational mentors.

To be sure, hagiographic treatments of Mandela's accomplishments exaggerate his role in key events. For example, FW de Klerk probably really does deserve his joint status with Mandela as a Nobel peace-prize recipient; his courage and initiative in helping to lead the democratic transition was as indispensable as Mandela's forcefulness, and the concessions he chose to make to his opponents were certainly comparable to Mandela's willingness to conciliate Afrikaners. Today, Mandela's reputation as the manager of South Africa's transition would be less secure if South Africa's democratic experiment had stalled: by and large it has not and the credit for that belongs to many people, including Mandela's less popular successor, Thabo Mbeki. Even so, Mandela deserves much of the credit for the relative civility of South African political life. In office he maintained a political style that engendered civic participation and democratic deliberation. Through his deference to legal constitutional proprieties, his predisposition for consultation and delegation, and his evident delight in everyday contact with ordinary people Mandela encouraged his compatriots to behave as assertive citizens.

The voice of leadership

True, Mandela had important collaborators that helped him to become a hero and he was the beneficiary of social context and historical circumstances. But no reassessments are likely to detract from Mandela's achievements as a political performer whether following his own strategic intuitions or acting out a collectively contrived script. Mandela's understanding of politics as performance is well documented - it is obvious and explicit in his courting of the media as early as the 1950s, and his fascination from that time with costumes and disguises. But Mandela's iconic status is not just the consequence of his theatrical capacity to motivate and inspire. His authority is also the product of the occasions when he has acted against the grain, when he has asserted his own individual will. Such actions have continued since his supposed retirement.

In a domestic South African setting, his embrace of HIV-Aids activism is an example of his willingness to challenge political convention: his charitable enterprise followed his challenge in 2001 of government policies within the ANC's leadership, a moment when he found himself painfully isolated. His statement on Zimbabwe on 25 June 2008 represents another instance of his willingness to transcend partisan orthodoxies - and what seemed a somewhat qualified reservation about a "tragic failure of leadership" can be read as much as a criticism of South African executive authority as a condemnation of abuses across the Limpopo.

Then there are plenty of instances of Mandela imposing his will upon an unruly movement during the transitional period of South African politics, between 1990 and 1994, not least in his insistence that South Africa should adopt a hybrid national anthem, incorporating verses from Afrikaner nationalism's Die Stem. In 1986, Mandela's decision to begin speaking to members of PW Botha's cabinet was his own and it was made against the advice of his fellow prisoners. Much earlier, in 1961, Mandela was the most influential voice in persuading reluctant ANC elders to sanction "armed struggle". In their own different ways each of these occasions represent instances when an individual shaped history powerfully with long-term consequences. There are enough of them to keep the historians arguing over Nelson Mandela's legacy for at least another nine decades.