Radar Detectors - Could One Have Saved Me?

I remember it well! I was on a fast stretch of road, but keeping to the limit for that stretch. I came towards a village, where the speed limit dropped by 20mph. Obviously I slowed down, and continued to slow. The road curved round to the left and went downhill. All this within about 100 yards of the slow down sign. And guess who was waiting for me at the bottom of the bend? Yes, you guessed it,