FWIW, I've suffered from similar pain in the past and I believe it is related to the sciatic nerve. It didn't make any sense otherwise to have a problem with every muscle down the back of one leg.
The sciatic nerve goes down from the base of your spine to your foot. You can get problems with it being pressed or rubbed by the spine, say if you have a disk slightly out of line, and the pain is felt down your leg rather than in your back.
I find that if I do some gentle back extensions and sit up straight for a few days it goes away again.
No medical professionals were involved in this diagnosis or treatment.
But were any animals harmed??
I wonder if this is what my bothersome hamstring has been caused by?
Liz says it's not sciatica as it stops miles above the foot.
I'll see how I go - see what physio says, but at £50 it's an expensive game....