Originally Posted by focusv8
O.K theory no. 2;
It was on a lorry full of scrap lorry bodies stacked very high, something shifted just before the driver got to the gantry, the body caught at the top, fell off and jammed, Corsa hit it, lorry driver didn't notice, or did and cleared off.
Looking at how dark it might have been I bet the Corsa driver just didn't see it against the dark sky, not the sort of thing you normally find abandoned on the motorways
I bet there will be some CCTV somewhere showing what lorry it was.
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Scrap body seems like a good call - looking at the pic a second time - it has no back door which is odd unless it was scrap.
I'd guess the concertina shaped thing at the top (against the gantry) is a sheet, but directly beneath the ARROW sign on the gantry, what are the two red rectangular shapes?