One of several clumps seen tangled in a mesh fence alongside the South West Coastal Path.
No interactions present.
... the only other option would be White Briony (Brionia dioica) which would look pretty similar at this time of year, but which would have the remnants of the tendrils, which the unrelated Black Briony lacks.
Both, incidentally, moderately poisonous - berries of both are described as strongly emetic, lovely.
How to take close-ups with cheap phone and hand-lens:
Field Guides for Budding Botanists:
Lat/Lng: 50.1932, -5.4422
OS grid ref: SW544382