Rainboe is correct!
It was gear collapse on wet grass! I happened to be there on that day. I am not sure of the runway directions but the first landed in a north easterly direction and had a gear collapse, stopping just short of the fence. A few hours later another came in and landed in a easterly direction, and the same thing happened, but this time the aircraft went through the boundary fence, finishing up on the Eastern Road, a dual carrigeway running down the eastern side of the airfield. I rememeber a local police inspector tried to get a bulldozer from the sand and gravel company nearby to tow that 748 back onto the airfield, by putting a chain through the rear door openings and pull it back to the runway to clear the road. I remember an argument ensued as to the wisdom of that, and I believe he was persuaded otherwise, but at that point I had to leave, so I am not sure of that particular outcome. Rumour has it that they did try to pull it back, but the chain started to slice through the structure, so the idea was abandoned!