For some reason I don't quite understand, drivers on English drive routinely drive at speeds that are unsafe for this narrow, winding road. While I'd like to believe that people are smart enough to gauge for themselves safe travel speeds based on the conditions at hand, recent events seem to indicate that some drivers will drive what they believe to be the speed limit regardless of road conditions, even to the point of losing control of their vehicles.
If drivers continue to demonstrate an inability to judge for themselves safe speeds on this road, I suggest that the engineers determine safe speeds for them and communicate this information using highway warning signs from the Manual of Universal Traffic Control Devices.
I recommend a W1-5 (Winding Road Warning Sign) shown here:
Combined with a W13-1 (Advisory Speed Plaque) shown here:
According to the driver who lost control of her vehicle at this location, she lost control while traveling at "25 m.p.h." under dry road conditions. To me, this indicates that the W13-1 Advisory Speed Plaque should display a recommended speed substantially lower than "25 m.p.h." I recommend 15 m.p.h.