Following a three-year break, the world’s oldest Grand Prix reappeared on the calendar with a two-day race at Dieppe over a distance of 956 miles (1,538km), making it the longest event of the century at that point. It was also the last race of the giant cars, many of which were almost as high as a man. Since the only entry specification was a minimum cockpit width of 175mm (6⅘in), an army of these monster machines was unleashed on the Dieppe circuit – 17-litre Lorraine-Dietrichs and 14-litre Fiats dwarfing the 7.6-litre Peugeots and especially the little Sunbeams which were competing in the 3-litre voiturette class for the Coupe de l’Auto. The latter was run in conjunction with the Grand Prix and attracted an entry of 33 cars. Despite a partial German boycott, there were 14 vehicles taking part in the Grand Prix (an Excelsior, three Fiats, four Lorraines, one Mathis, two Rolland-Pilains and three Peugeots), making a total of 47.
With size considered to be everything, the clear favourites were the Fiats and the Lorraines. Among the Fiat drivers were the American amateur David Bruce-Brown and fellow countryman Ralph de Palma, who was due a change of luck. The previous month he had looked a certain winner of the Indianapolis 500 until his engine failed with two laps remaining. De Palma and his mechanic, Rupert Jeffkins, bravely pushed the car towards the finish, only to be overtaken.
During the week prior to the race Dieppe was invaded by motor racing fans of all nationalities. The casino did excellent business and the authorities organised a series of boxing contests to entertain the visitors. Hotel accommodation was at a premium, rooms being let for four days only – two days preceding the Grand Prix and the two days of the race itself. So anyone wishing to stay for just two days had to pay for four. As a result of this blatant exploitation, many followers preferred to camp out around the circuit.
The cars were flagged away from 5.30a.m. at 30-second intervals in front of a packed grandstand even at such an early hour. Victor Rigal’s Sunbeam was first away for the voiturettes and Victor Hémery in his huge Lorraine was the first Grand Prix car to start, at 5.33. Hémery was also the first to reappear at the end of the opening 47 mile (75.6km) lap at 6.12a.m., but the race leader was Bruce-Brown in the Fiat S74, who came round ten minutes later having taken 37min 18sec for the lap. Georges Boillot was second in a Peugeot with Hémery third and Jules Goux fourth in another Peugeot. Hémery suffered engine failure on the second lap and a lap later Goux dropped from third to fortieth so that after five laps (quarter-distance for the race), Bruce-Brown led from Boillot and Louis Wagner’s Fiat. The leading positions remained unaltered for the rest of the day and at the end of that ten-lap session, Bruce-Brown led Boillot by 2min 1sec with Wagner nearly half an hour back in third. A highly creditable fourth was Dario Resta in a little Sunbeam. A total of 19 cars were still going. Bruce-Brown’s driving had been a revelation, particularly his smooth, fast cornering. Nowhere was this more evident than at the S bend near the railway bridge at Ancourt, where a bugler was stationed to give audible warning of each car as it approached. The Fiat cars had on the whole been very impressive, too, being described as ‘running with gyroscopic steadiness as solidly as the proverbial rock’. Their Achilles’ heel, however, was pit stops. Although the new tarred road surfaces represented a vast improvement on the old dirt tracks, the Fiats were extremely hard on tyres and had to stop for regular wheel changes. The Italian company had made the mistake of persisting with fixed wooden wheels with detachable rims instead of the newly invented detachable wire wheels with knock-off hubs that were favoured by Peugeot. As a result Fiat pit stops were considerably longer than those of Peugeot. Fiat also lost valuable time refuelling by churn and funnel, whereas Peugeot used a more advanced pressure system. So despite the fact that the Fiats were markedly quicker on the road – as would be expected from their superior power – the delays caused by pit stops kept them within reach of their French rivals. Nevertheless Bruce-Brown, in his familiar woollen windsock hat, was in pole position and was confident of cementing a famous victory on the second day. The cars started the second day at the intervals and in the order in which they had finished the first … minus René Hanriot’s Lorraine which had mysteriously caught fire overnight. The race conditions had also changed during the hours of darkness, persistent rain having created a slippery surface which suited Boillot better than Bruce-Brown. Consequently the Frenchman steadily whittled away at the lead until after two laps on the second day (12 overall), Bruce-Brown’s advantage was down to a mere 11 seconds. Bruce-Brown was still ahead when, out in the country, his car had the misfortune to collide with a stray dog, an impact which ruptured the fuel tank, causing it to leak. As he struggled to carry on, he was promptly disqualified for refuelling away from the pits. De Palma and Goux fell foul of the same rule.
Profiting from the hound’s intervention, Boillot moved into first place and stayed there. His only worrying moment occurred on the penultimate lap when the Peugeot suffered a jammed gearbox. It took Boillot and riding mechanic Charles Prévost 20 minutes to fix it and they set off again, but with only second and fourth gears. Fortunately Boillot’s lead was such that he was able to coast home by 13 minutes from Wagner with Rigal third and Resta fourth. By finishing third, fourth and fifth overall, the Sunbeams easily won the Coupe de l’Auto. As for Bruce-Brown, he kept going to the finish despite his disqualification, but never again would a car of over 10-litres come so close to winning a classic road race. And later that year he was killed during practice for the US Grand Prize at Milwaukee.