But that was precisely what happened at the Queen's Birthday Party in June after President Mandela's speech in which, apart from wishing 'Her Majesty' another 42 years on the throne, he expressed his delight at being in the company of so 'illustrious' a South African as General Viljoen.
Much of the chatter in parliament these days centres on the extraordinary rapport that has developed between the President and the general, the leader of the Afrikaner Freedom Front. An African National Congress member of cabinet summed up prevailing sentiment when he exclaimed: 'It's a love affair]'
A brief examination of the two men's backgrounds reveals that until recently they clung to positions no less antagonistic than the head of the British Army and the leader of the Provisional IRA. While Mr Mandela was being sentenced to life imprisonment in 1964 for leading the ANC's 'terrorist' effort, the young Viljoen - 15 years Mr Mandela's junior - was pursuing a meteoric career in the South African Army which would see him rise, by 1980, to the role of overall commander of his country's armed forces. As such, General Viljoen oversaw South Africa's surrogate wars in Angola and Mozambique, murderous cross- border raids against ANC targets and the creation of clandestine units to strike against ANC activists inside the country.
He retired to his farm in the Eastern Transvaal in 1985 and only re-entered the public arena in May 1993 when he created the Afrikaner Volksfront, a political organisation linked to Eugene Terreblanche's Afrikaner Resistance Movement (AWB) by a common dedication to the secessionist idea of a Boer 'fatherland'.
'An Israel for the Afrikaners' was his battle cry as he toured the country warning the volk to 'polish their weapons' in preparation for war against the ANC 'Communists' whose leader, Nelson Mandela, was orchestrating the bloodbath in the black townships to 'seize' power.
Then, towards the end of last year, talks began with the ANC leadership. General Viljoen met Mr Mandela and began to reconsider his assessment of the man. In time it began to dawn on him that perhaps he had more in common with the ANC leader than with the yahoos of the far right. The inglorious 'battle of Mmabatho' in March this year, when the AWB 'kommandos' were routed by the Bophuthatswana army, persuaded him that the best hope for 'Afrikaner survival' lay in abandoning the war talk and taking part in the elections. Today the re-named Freedom Front has nine MPs in the 400-seat parliament.
South Africa's Hansard records that in his maiden speech on 25 May, General Viljoen, addressing himself to the ANC's 'Madam Speaker', said: 'I want to begin by referring to the honourable President's Presidential Address. I want to thank him for the few words that he spoke in Afrikaans. How long he spoke in Afrikaans is of no consequence; what matters is the spirit in which he did so - the spirit of reconciliation.'
There is a political logic to General Viljoen's loyal - not to say affectionate - opposition. The government has agreed to the establishment of a state-funded 'volkstaat council' in which he and other right-wing Afrikaners are debating the question of self- determination. Mr Mandela, for his part, never ceases to describe General Viljoen as 'an honest man' and 'a great politician' because he is deeply grateful to him for having effectively defused, almost single-handedly, the right- wing terrorist threat.
Trim, white-haired, courteous, they are men of the times who belong, in spirit, to an earlier generation. A senior diplomat who knows them well observed how at home they had appeared at the Queen's Birthday Party. 'They're very civilised, in the old-fashioned sense. Nelson Mandela has an endearing attraction for the world as it was 30 years ago - for example in his affection for the British Empire and values as they used to be, values which Viljoen exemplifies.'