Dominique de Villepin, the Prime Minister, is officiating at the ceremony at Chauconin-Neufmontiers, which finishes the £2 billion route of the TGV-Est, the eastern train à grande vitesse. Trains running at up to 200mph (320km/h) will put Rheims within a 45-minute commute from Paris and bring Strasbourg within 2 hours 20 minutes instead of 4 hours.

The imminent arrival of the link has boosted property prices along its stops. It is likely to knock out airline services between Paris and Strasbourg and Metz, in the same way as it has taken most of the traffic between Marseilles, London and Brussels. The completion of the eastern line, which crosses the vineyards of Champagne, has been timed to coincide with festivities for the quarter century since the late President Mitterrand opened the first TGV, between Paris and Lyons, on September 22, 1981. A show with two full-scale mock-ups of the sleek blue and white trains opens by the Eiffel Tower at the weekend.

While France is beset by gloom and economic uncertainty, the TGV is being celebrated as a triumph of Gallic vision, with no match except for Japan’s older and less flexible network of Shinkansen.

“The legend goes on,” said Guillaume Pepy, the deputy chief of SNCF, the state railway, as politicians crowded in to share the credit. In another anniversary act, SNCF tested TGV trains at 225mph on the Mediterranean line on Monday with a view to raising their cruising speed. (The fastest British trains do not exceed 125mph). The 1,250-mile (2,010km) TGV network, a product of the French tradition of centralised power and state engineering, has transformed life, bringing cities such as Tours, 230 miles from Paris, within commuting range. A daily season ticket on that TGV route costs £390 a month. Between Paris and Lille (127 miles each way), daily commuting costs £415 a month. Vendôme, 260 miles to the southwest of the capital, has become a dormitory town. About 400,000 people use the TGV for daily work.

The TGV project, which was launched by the late President Pompidou in 1974, has brought northern prosperity to the Mediterranean and Atlantic regions as well as opening them to weekend tourism from Paris. The opening of the service to Avignon and Aix-en-Provence in 2001 brought a flood of second-homebuyers into Provence, now under three hours from the capital.

“The TGV is the Concorde plus commercial success,” Clive Lamming, a railway historian who wrote the Larousse des trains et des chemins de fer encyclopaedia, told The Times. “The TGV has virtually reduced France to one big suburb. This has increased the independence of businesses from Paris. Workers are more mobile and their costs are less.”

The TGV runs on separate high-speed lines that keep it away from the mixed traffic on which fast trains in Britain and elsewhere operate.