On the way I started having problems with gear changes and on arriving at the car-park lost them all except I managed a crunching reverse.
Stuck out on the road on a bend I quickly high tailed backward knocked down a road marker and landed in a ditch but safely off the road. No damage only a bent plastic road marker.

I immediately lifted the bonnet and adjusted the cable.
That solved the problem until I arrived home when again I lost the ability to gear change. I again screwed in the nuts this time all the way possible.
My question is why is this happening? The clutch hasn't been slipping.