The preferred temporal structure of the isolated diphthongs /ai/ and /au/ in Southern English is examined by a means of paired comparison test using a comprehensive range of dynamic trajectory variants. This is compaired with the temporal structure of those diphthongs produced by 10 speakers of Southern English. Results indicate a clear language-specific trajectory, differing from those found in tests with German and Dutch listeners. The English production data are more complex in their manifestations, but many tokens approximate the same language-specific dynamic structure.