ɐ ɹˈɛd ˈɑːɹ θɹˈiːhˈʌndɹɪd nˈaɪnti pɹˈoʊɾoʊtˌaɪp ˌʌndɚwˈɛnt wˈɪnd tˈʌnəl tˈɛstɪŋ ænd ˌɛɹoʊdaɪnˈæmɪk ɪmpɹˈuːvmənts ɪn ˈɪŋɡlənd, haʊˈɛvɚ, ðə fˈaɪnəl kˈɑːɹ wʌz bˈɪlt ænd tˈɛstᵻd ɪn ˈætsuːɡi, dʒəpˈæn.
A red R390 prototype underwent wind tunnel testing and aerodynamic improvements in England, however, the final car was built and tested in Atsugi, Japan.