I’m not generally the sort of person who lies awake worrying the attic floor will collapse because one more storage box has gone up there. Nor do I usually step onto a balcony wondering whether this is the exact moment it detaches itself from the building.

Most of us don’t think like that. We assume buildings obey the laws of physics. We live, after all, in a country with world-class engineers, detailed standards and enough structural calculations to make your eyes glaze over.