How to factory reset the Brompton advance 4 speed gearing

Please note from October 2023 a running production change means the bigger sprocket on the cassette will be 20t not 18. Electric C Line produced after October 2023 come supplied with the Advance 4 speed gear system. Please note: the pinch bolt must be tightened to 4Nm. For more help: https://www.brompton.com/support/4spe...