The race was won by Johnny Hindmarsh and Luis Fontés in a British Lagonda, breaking the run of four consecutive Alfa Romeo victories.
A strong quartet of privateer Alfa Romeos, including previous winners Raymond Sommer, Earl Howe and Luigi Chinetti, were the favourites.
Sommer initially had the lead for most of the first quarter of the race, until delayed by engine issues and, with his co-driver too sick to drive, he retired.
As a drizzly dawn broke, it was the Alfa of Pierre Louis-Dreyfus only a half-lap ahead of the Lagonda, and the lead continued to swap through the morning as the two cars pitted.
To avoid controversy and argument, this year the Automobile Club de l'Ouest (ACO) introduced a mathematical formula to calculate the target distances for the Index of Performance.
[2] As an incentive, the French Office National des Combustibiles Liquides offered a FF10,000 bonus prize to a team who won either the Index of Performance or Biennial Cup using the ternary fuel.
Having matched Bentley the previous year with four wins apiece, Alfa Romeo was keen to go one better and become the most successful make at Le Mans.
As well as the venerable La Lorraine and outrageous Duesenberg, the large-engine classes saw the arrival of new teams to challenge for outright victory: the French Delahaye and Talbot, and British Lagonda.
After one of the highest number of finishers in the previous year's race, there were sixteen cars turning up to contest the Coupe Bienniale.
The British lord, Earl Howe (running with Brian Lewis, Baron Essendon) brought his three-year old Alfa that he ran the year before.
[11] Three French Bugatti drivers, Max Fourny, Albert Blondeau and Bernard Chaudé had formed a new racing team.
The Écurie Argo had two entries: a 2.3-litre Type 51 modified with aerodynamic bodywork over the rear suspension would be driven by Fourny and Chaudé.
Fox had one car for his team regular Squadron Leader Johnny Hindmarsh and new member Luis Fontés (English son of a wealthy Portuguese shipping executive), while the other had former "Bentley Boy" Dudley Benjafield alongside Sir Roland Gunter.
Encouraged by wealthy heiress Lucy O'Reilly Schell to develop a car for hill-climb racing, the company set up a competition department.
Six new cars had been built modelled on the new Riley Sprite mechanical set-up, two of them fitted with its "12/4" 4-cylinder 1496cc engine tuned to put out 70 bhp.
The second, entered under the name of Dorothy Champney (Victor Riley's wife), had the all-female pair of Kay Petre and Elsie Wisdom.
The works team was not present but three international privateers were entered: John Ludovic Ford and Maurice Baumer returned for a third time, and were joined by the cars of French car run by Philippe Maillard-Brune (who had recently won the Bol d'Or race three weeks earlier) and Dutchman Edmond Hertzberger.
Maurice Falkner had acquired an ex-works Aston Martin and had won his class in the Mille Miglia this year with Tommy Clarke.
His co-driver was Alf Langley, while Stan's brother Donald again raced with journalist Tommy Wisdom, and Norman Black/Roddy Baker ran the other two cars.
[23] This year, the MG company worked with well-known speed-record champion George Eyston to prepare three all-female crews to run the Midget PA in the 1-litre class.
[27] This year raceday started grey and drizzly, however as the cars formed up on the grid en echelon, the rain eased.
[8][30] During the Alfa's ordeal, Hindmarsh was able to move the Lagonda to the front followed by Stoffel, Labric's Bugatti, Howe and Gastaud all on the same lap.
Encouraged on by the partisan crowd he went back out for two more laps, but facing a hopeless situation alone with a sick car, he pulled in again and retired.
[31] Then abruptly over the course of an hour, everything changed: Three laps later Veyron's Bugatti broke its rear axle, and the suspension on Chinetti's Alfa failed.
[31][17] Soon after that, Stoffel pitted the Alfa to fix a misfire and a water leak, losing seven minutes fitting new spark plugs.
They finished ninth after a late-race contest with Falkner and Clarke's privateer Aston Martin ended up with them less than half a lap behind.
[18] The Singer–MG battle in the 1-litre class went the way of the former, with racing manager Stan Barnes, and Alf Langley, winning by 11 laps from the SIMCA-Fiat of Anne Rose-Itier.
In what turned out to be the last outing for the model, the team covered the furthest distance yet for a BNC (by 10 laps) and just missed taking 4th in class by 5 kilometres.
[24] Two of the little Austins were the last finishers, covering less than two-thirds of the distance of the winner, with the privateer John Carr beating home the works car.
[4] In contrast, Anthony Lago completed the purchase of the Talbot company, and the success for Amédée Gordini convinced SIMCA to appoint him in the new year for their blooming racing program.