It turns out that the ugly smoking shelter in the car park was once a fine looking covered area at the rear of the barn.
Here it is in the car park:
And here is the same shelter behind the barn a couple of years earlier courtesy of Google street view. The mounting holes for the frame were still there, and the original location explains the non symmetrical shape.
We had to move the shelter from the car park so that the new build next door could connect with our sewer. We’ve put it back where it was originally and it works brilliantly. In France a covered outdoor area would be called a Tonnelle (not a smoking shelter).