This is Day 1 (out of two) of the February 1981 TGV World Speed Record. A TGV set was secretly prepared for high speed tests. A secret that was poorly preserved as many railfans knew it. Today, it would be even worse with the Internet. Fresh from the manufacturer since its delivery date was October 22 1980 and its official receipt in SNCF inventories was November 14 1980, the #16 TGV trainset was modified as a race train and equipped with a laboratory car. The set had only 7 cars instead of 10, a higher gear ratio of 1.702 between the traction motors and the axles, and all power wheels had a larger diameter to facilitate reaching higher speed (6 first axles on each end). Thus the second and the second to last cars were slightly slanted because they were lying on power axles on one end and non-power axles on the other end.
On that day, a (useless) deception was attempted to take the press at bay: the trainset markings were changed to #33 instead of 16. But only the bigger markings were changed, not the smaller ones on the power cars, still showing the numbers 23031 and 23032 associated with the trainset #16. The train would run as mock-up #33 for the rehearsal day (Feb 25 1981) and back to normal as #16 on the next day. Interestingly, the #33 was not yet built: it will be officially received by the SNCF, new from the Alsthom factory several months later, on June 9 1981!
The picture shows one of the test runs of Day One, when the old 331 km/h World Speed Record of March 1955 was broken for the first time in 26 years. On that day 5 test runs reached 300, 325, 340, 363 and 371 km/h. Then on February 26 1981 the record will be safely set at 380 km/h. A SNCF General Manager was on board and preferred not taking any risk running at a higher speed, which was probably feasible. This record will then be broken 5 times (4 times officially by the German ICE, and by 2 different TGVs, and one time unofficially) until the 574.8 km/h of 2007.