Appropriate signage

I live on what used to be a Roman Road but now is an unadopted farm track. We only have 2 seasons a year. The muddy season and the dusty season. It’s full of pot holes and occasionally in winter it is impassable.
However, Sat Nav thinks its a main road and some HGV drivers think its a short cut. They have a bit of a job turning into the lane for a start and then after a hundred yards they realise the mistake. Now they cannot turn round and have to reverse their 40 tons back. Fortunately HGV drivers are usually quite adept at reversing those huge trailers and i stand at the gate and smile at the drivers quietly whispering plonker through my teeth.
So when i saw the sign below i thought it was quite appropriate. I wonder who gets the £100? And do they pay tax on it?