"To know and not to do is not to know" - Proverb.
I still remember learning to drive. In particular I remember that most tricky of manoeuvres, the hill-start. It was a warm summer's evening as I sat there in the driver’s seat, parked on a precipitous hill listening to my instructor patiently explaining the technique.
Handbrake on, engage first gear, easy on the accelerator and a little bit of clutch, watch the bonnet rise, off with the handbrake, a little more clutch, a little more accelerator and move smoothly off.
I repeated it back to him, all nine steps. I had it word for word, no problem. Then I started the engine and almost immediately, there was a problem!