Amid vicious recrimination, in which Mr Le Pen accused one of his daughters of "family betrayal", the NF broke into two mutually loathing factions, each claiming to be the true standard-bearer of the French ultra-right. Ending weeks of clandestine civil war, Mr Le Pen, 70, finally moved directly against Bruno Megret, the increasingly powerful second force in the Front. He suspended him from his job as delegate-general of the party and accused him of "crimes against the NF and against France". He also repeated on national television his accusation that Mr Megret's supporters were "racists" and "extremists", in effect conceding something he has always denied: that the NF feeds on racial bigotry.
Mr Megret, 49, who represents a more managerial, modernising as well as deeply xenophobic force in the NF, refused to accept his dismissal. He will go ahead with plans to call an emergency conference next month when those who attend will, doubtless, elect him as president of a kind of Provisional Wing of the NF.
Mr Le Pen, NF president since its creation in 1972, remains in control of party headquarters in the Paris suburb of St-Cloud, from which all Megret supporters were ejected on Wednesday night. But Mr Megret claims, perhaps with some exaggeration, to have the backing of more than half the local and regional bodies of the party and substantial support among grassroots NF voters.
He may also have a lot of dirt on Mr Le Pen, who was reported to be alarmed to discover Megret sympathisers had been downloading information from the St-Cloud computers in recent days. Mr Le Pen had ordered all NF bank accounts to be frozen two days ago. The opaque finances of the Front and the sources of his lavish lifestyle have always been mysteriously entwined.
The Le Pen-Megret show-down, long expected, is partly generational, partly tactical. It is also a question of personal ambitions and clan hatreds within the Front, which has always been an extraordinary coalition of antagonistic groups (high Catholics, pagans, Vichy sympathisers, colonial nostalgics, extreme nationalists, Europhobes and outright racists). Mr Megret supporters, mostly young or middle-aged, believe they can release the party from the ideological ghetto created by Mr Le Pen and form electoral alliances that would bring far-right ideas, and themselves, into the mainstream of French politics and government. Mr Le Pen and his supporters, including most of the old guard but also many younger activists, accuse the Megretistes of being prepared to trade the party's ideological purely for a few cabinet posts.
Most of all, perhaps, the struggle is about Mr Le Pen's refusal to accept he is growing old and that the success and growth of the NF mean it is no longer his personal fiefdom. The schism cuts through the heart of his family. On television on Wednesday he accused Marie-Caroline, the eldest of his three daughters, of "betraying her family" by being linked to "one of the leaders of sedition". She lives with one of Mr Megret's lieutenants, Philippe Olivier, and has tended towards the Megret side in recent days.
There is bitter irony here. The internal crisis in the NF began when Mr Le Pen was suspended from seeking public office because of his assault on a socialist female candidate during last year's parliamentary elections. "Papa" was campaigning for, and alongside, Marie-Caroline at the time.
Is this the end of the National Front? Should all democrats and anti- racists rejoice? No and yes. The far right is a rooted presence in the political psyche of France; its strength has tended, however, to wax and wane with internal splits and quarrels. This week's events may well mark the start of the end of the Le Pen era and halt the slow rise of far-right influence, which began with Mr Le Pen's big breakthrough in the European elections of 1984.
He remains the single most compelling figure of the ultra right and one of the country's few charismatic politicians. He will continue to command a large share of ultra-right votes. But a long period of internecine warfare with Mr Megret will rob him of his image as a man of the people. The effect is likely to be a collapse of the overall far-right vote - up to 15 per cent in recent elections - as non-militant fringe voters drift back to the centre-right and even the Communists. This would transform the French political landscape and, above all, revive the fortunes of President Jacques Chirac and the centre-right.
Mr Megret's chances of building a successful counter-movement are uncertain. He is a highly intelligent, subtle and presentable politician. But he has none of Mr Le Pen's vulgar humour or rumbustious charm. His only chances of success would seem to be to deliver a knock-out blow against Mr Le Pen, possibly with some startling revelation about the NF's finances or wider neo-fascist European connections.
In the past month Mr Le Pen has been waging a campaign of harassment against Mr Megret and his supporters, stripping them of responsibilities, even firing several people who worked with Mr Megret on spurious cost- cutting grounds. Last weekend Mr Megret struck back. He managed to smuggle his fired and suspended supporters into a meeting of the NF national council. To Mr Le Pen's astonishment, their presence was applauded by a majority of those present. When he ordered them to be ejected from the hall, Mr Le Pen was booed and heckled.
This week harassment became a purge, with Mr Le Pen striding the corridors of NF headquarters, suspending or ejecting officials he suspected of pro-Mr Megret sympathies. On Wednesday Mr Megret made what amounted to a first, frontal attack on Le Pen's authority, backing his supporters' calls for an extraordinary congress of the party next month to resolve the quarrel.
Mr Le Pen had already made clear that anyone who backed such a congress would be regarded as an enemy of the party. Later that night he suspended Mr Megret from his job as delegate-general. Calling for such a meeting was "a crime against the NF and above all a crime against France".