Chatteris is mainly a Microlight/Parachute centre airfield and has a large number (can't remember exactly how many and I can't find my airfield plate) of grass runways with varying orientations. They are all pretty short. G-OWIN, the parachute centre's Islander has no problems but when I planned to fly in in my Arrow to watch my daughter do a charity sky dive I decided they were all a bit tight and went by car.
I've seen these poles: IIRC they are at the threshold of the longest runway and as they are on the farmers property they are quite legal.
Don't know what type of A/c crashed but he could just have run out of runway, having been forced to use a shorter runway.
The farmer adjacent to Crowfield in Suffolk did a similar thing by stacking hay bales at the end of their runway a few years ago.
There are some real t*ssers out there, but perhaps the farmer was just p*ssed off by the constant sound of the drop a/c staggering to 10000ft every half hour all day all weekend.
His farm was there long before the airstrip.
Happy flying
Cusco