British Rail Class 373 Eurostar

The Class 373 Eurostar was the original fleet of high-speed electric multiple units built for the Eurostar international passenger services through the Channel Tunnel, linking London with Paris, Brussels, and other European destinations. Thirty-eight trains were built between 1993 and 1996 by GEC-Alsthom (later Alstom) at their works in Belfort, France and Birmingham, England, based on the proven technology of the French TGV but substantially modified to meet the unique requirements of operating over three different electrical systems and through a safety-critical undersea tunnel on a route that crossed three countries.

The engineering challenge of the Class 373 was formidable. A Eurostar train departing from London Waterloo (and later St Pancras International after 2007) would begin its journey under 25 kV 50 Hz AC overhead from the BR electrification; enter the Channel Tunnel under the tunnel's own 25 kV 50 Hz AC supply; emerge in France and switch to the SNCF system's 25 kV AC on the high-speed lines north of Paris; and when running to Brussels, transition to the Belgian national railway's 3,000 V DC overhead on classic Belgian lines. This three-voltage capability required traction equipment of considerable complexity, and each power car carried sophisticated switchgear and rectification systems to manage the transitions automatically as the train crossed the supply boundaries.

Each Eurostar train was an eighteen-car articulated formation with two power cars at either end and sixteen passenger carriages between them. The articulated construction — shared between adjacent bogies rather than one bogie per vehicle — was derived directly from TGV practice and gave the trains their exceptionally smooth ride. The passenger accommodation was divided into First and Standard classes across the sixteen coaches, with a buffet/bar car at the centre. At full length a Eurostar train was 394 metres long and carried up to 794 passengers. Three ‘half-sets’ of nine cars were also built, numbered in a separate series, for shorter services.

Eurostar services began in November 1994 with the journey time from London Waterloo to Paris Gare du Nord of approximately three hours. The service was an immediate success despite early teething problems with the complex multi-voltage electrical systems, and passenger numbers grew steadily. The opening of the High Speed 1 line in stages between 2003 and 2007, replacing the slow approach from the Channel Tunnel portal at Folkestone to London via conventional Southern Region tracks, reduced the London–Paris journey time to two hours and fifteen minutes and transformed Eurostar's competitive position against air travel on the route.

From 2015, the Class 373 fleet was progressively replaced by the new Class 374 Velaro e320 sets built by Siemens, which offered higher capacity and speed. Some Class 373 sets continued in Eurostar service until 2018, by which point the last examples had been retired. Several power cars have been preserved: a pair is at the National Railway Museum in York, and further examples are held at other locations. The Class 373 represents one of the most technically complex railway vehicles ever to operate in Britain, and the beginning of an international high-speed rail link that fundamentally changed travel between Britain and continental Europe.