If the French government did not know what it was up against in trying to reform the social-security system, it does now. For five hours yesterday, a column of up to 50,000 demonstrators marched through central Paris, paralysing traffic in the city's commercial district on the right bank of the Seine and drawing bemused exclamations of "Amazing!" and, at times, warm applause from onlookers massed on the pavements.
Arranged in almost tribal formation, union by union, each with its own coloured banners and battle-chants, the demonstrators processed slowly in some disorganisation, mingling cries of "Chirac and Juppe - Out, Out, Out!', angry drumming, and snatches of French popular songs reworded to protest against "butchery of the social-security system".
Big stores had barred their doors, but small shops and cafes, whose owners could be heard debating loudly whether to shut for safety's sake or stay open for the sake of business, did a roaring trade.
The accompanying strikes brought many of France's internal and external transport links to a standstill. Air France managed to operate fewer than one in five of its short-haul flights; some provincial French airports managed no flights at all. There were neither flights nor ferries to Corsica, which was cut off for the day.
Cross-Channel links were badly disrupted. There were no ferries from Calais: French-operated ships remained in port; British ferries were rerouted to Belgian ports; no cargo ships sailed at all. Other ports, however, including Dieppe and most of those farther west, worked normally.
Although the Channel Tunnel shuttle trains operated without a hitch, the Eurostar service was unable to run the 10 out of 12 Paris-London trains it had confidently predicted the previous day. The first two trains due out in the morning were prevented from leaving by two dozen or so pickets who blocked the line. Eurostar laid on coaches to transport passengers to Folkestone via the shuttle, but by 11am only three coaches had left.
The departure board at the usually bustling Gare du Nord was blank. Some high-speed trains did run on major French routes, but only a fraction of the usual number. Suburban train networks into Paris and other big cities were in effect shut down.
By mid-afternoon only one of the 12 Paris underground lines was operating; and fewer than 10 per cent of buses. The morning rush-hour had seen improbable traffic jams at the entry points into central Paris, and drivers were expecting a repeat performance in the evening. The picture was repeated across France.
According to official figures produced by the public-service ministry, yesterday's strikes were less well supported than the public-sector strike on 10 October, called to protest against the government's declaration of a public-sector wage freeze for 1996.
However, the disruption to transport by the end of the day, and the scenes on the streets, told a different story. While most banks managed to stay open, post offices, benefit offices and labour exchanges were all shut. And if - which is open to question - more people turned up at work than on 10 October, considerably more people also turned out on the streets to demonstrate.
In late morning, President Jacques Chirac, and the Prime Minister, Alain Juppe, whose plan to reform the health and social-security system was the object of all the protests, held an unscheduled meeting at the Elysee. Mr Juppe left without saying anything, but the labour and social affairs minister, Jacques Barrot, later said in a radio interview that the government wanted to restart a dialogue "to exorcise the fears expressed by the demonstrators and strikers".
It was Mr Barrot who, in September, announced the 1996 pay freeze in the public sector and said that he had no plans to discuss the matter further.
Until yesterday, the government's position looked strong, and the trade unions, most of whose support is concentrated in the country's large public sector, which looked disunited and weak. Only six of the seven main unions had sponsored yesterday's strike, and the leadership of the biggest union, the CFDT, was squabbling in public about the merits or otherwise of Mr Juppe's proposed reforms.
Yesterday, however, "people power" dominated. Although the second-largest union, the Force Ouvriere, had told its members to save their energies for their own day of action next Tuesday, FO members supported the strike and formed one of the biggest contingents at the Paris march.