This greenhouse just isn't up to the Mayenne weather. Today threatened thunderstorms, and although we never got a torrential downpour, we did get some strong winds. These can cause to break or bend, the plastic joints holding the metal struts of the greenhouse together.
I had been holding the cover down with big rocks but they weren't doing the job so I let the cover blow off and lie on the ground. Better that than a knackered frame. Meanwhile I dug over the rest of the soil in the greenhouse, getting the rocks out. Frankly it was better to work in the open air than in the 38° heat inside.