The Old Dalby test track.
According to Greenpeace, the engine itself was unbolted so that it would "roll over" the container.
You couldn't make this stuff up.
The conspiracy theorists claimed it did leak and was strategically positioned in such a way to withstand such force. Another was that the loco had been weakeaned to lessen the impact. It used to be on display at NRM, I remember seeing it as a child.
I'll just leave this here: