For the public record...

Residue of GCC inaction on grass plot.

You were warned local builders were using the council land for storage. You did nothing. You were forewarned they would fly-tip when the job was done. You did nothing. Their inevitable flytipping was reported. You did nothing. I contacted my councillor. You then removed their builder's bag and other rubbish... and left this.

All of which could have been avoided if you had simply intervened in the first place - Planning would have had details of those responsible.

GCC - their own worst enemy.