Before the name was usurped by a mobile phone, this meant only one thing, and they're at their peak right now. We collected some last weekend and I made eight blackberry and apple crumbles for the freezer. Yesterday we filled Miss Z's bike basket with more blackberries and her younger sister is currently demolishing them, conveyor-belt style.
So get out on your bike down remote lanes, which haven't been plundered yet, and fill your boots. Or your panniers. The bigger the "bobbles", the sweeter they are.