De Rosier's chief rival was Charlie Collier, still smarting from his second place disqualification in the island race. As De Rosier was the acknowledged champion of the United States, and Collier had already made several unbeaten records at Brooklands, there was much public interest in the forthcoming match races between the two, scheduled for July. De Rosier prepared one of the factory 61 cubic inch twins, installed in the usual short wheel based board track frame. No change speed gears were fitted, the drive being direct through a countershaft, without a clutch. Collier's machine was, of course, one of his own Matchless models, with a 61 cubic inch overhead valve J AP V twin fitted with direct belt drive.
The two champions were to race over distances of two, five and ten laps and were escorted by a starter's car for flying starts. The initial two lap race was a close contest. De Rosier allowed Collier to take a slight lead, taking advantage of his slipstream nearly the whole distance. Just before the finish, he pulled ahead with a burst of acceleration, and won by only a length at 80.59mph. In the five lap event, De Rosier employed the same tactics, but blew a tire in the fourth lap at nearly 90mph. With superb riding skill he was able to halt his machine without a fall, but, of course, was forced to retire.
The third two mile event was equally exciting. The two contestants ran closely for nearly the entire distance when, on the last lap, a spark plug wire came loose on Collier's engine. He managed to replace it while running at reduced speed, but in the meantime De Rosier had built up a substantial lead. By a heroic effort, Collier nearly caught up with him, but De Rosier won at 84.5mph. The contest was an interesting comparison' of two varied styles of racing. Collier's habit was to attempt an early lead and hold it all the way. De Rosier's strategy was to nurse his engine carefully until the last lap, and employ the slipstream technique, wherever possible.
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