What's the point of speed records?

A French TGV has smashed the world speed record for a train on conventional rails, hitting 356mph. But it cost a packet and required months of precision track work, so why bother?

French rail chiefs hailed it a triumph, while President Jacques Chirac said it was "new proof of the excellence of the French rail industry". The driver, Eric Pieczac, said it made him feel "very happy".

When the TGV train hit 356mph on track between Paris and Strasbourg on Tuesday, it shattered a 17-year-old record and was almost as fast as a World War II Spitfire at top speed.

It's very impressive, but 30m euros (£20m) had been spent specially modifying the 120-mile section of track. The train was powered by two engines, needed special wheels and went twice the maximum speed of a TGV on any passenger route. So what are the point of speed records?