Having made five jars of blackberry slop, I invested in some jam sugar and made three jars of jam today. Magic pectin!
The blackberry slop is pleasant enough with yogurt or added to apples as a pie/crumble filling, but does not do the job of jam.
The allotment site has a vast patch of blackberries, so I may make some more tomorrow. Time to squirrel away food for the Autumn/Winter.
When things get busy at work I console myself that at least I have home cooking.