Yes - we're thinking about setting up some CCTV. I think I will start that on another thread.
the council tried that where we used to live in Herts to try to stop the travellers fly tipping (you couldnt get prosecutions as they would block both ends of the lane with their transits first so the third one could tip unwitnessed) and the travellers stole the CCTV camera (!) and put it up it on their (council run ) site to stop other travellers stealing their cock fighting birds or their stallion, the camera only stayed in place for 3 days before that happened......
Every field had boulders or tree trunks to try to stop illegal dumping of waste and loads of horses being left tethered on it or the kids trashing the crops with scrambler bikes.
I now live elsewhere!
I would suspect this soil is from a casual landscaping job, like most of the rest of flytipping it is unregistered traders operating out of transits with just mobile numbers and no waste transfer licence, taking advantage of most peoples desire for the cheapest quote no questions asked about what happens to the waste. The gates interference is attempted theft for the scrap value. Make sure one hinge is reversed so it cant be lifted off easily, padlocks not much use as they always carry bolt cutters (sometimes even circular saws) as part of their working tools. Spray paint the gate a distinctive colour to make it more identifiable if they are stopped with it.
I wouldnt keep horses anywhere away from a supervised yard or my own home. Just couldnt take the worry.