Could very well be, @Borderline - The leaves don't seem to be quite the same as Black bryony when zoomed-in. Some good close-up photo's of the Fallopia leaves and flowers here:
Thanks both - yes, it does look like black bindweed. I'm guessing, as much as I'm into natural, wildlife/wildflower gardening, I should hoick it out - before the geranium gets strangled!
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