This was a vine that was flowering prolifically. Though I didn't notice an odor of the flowers, there were many insects feeding. It was growing on a hillside with many other tall bushes and small trees. There is a spring that keeps the ground moist for most of the year.
Along towpath near market st. I didn't/shouldn't take a specimen and didn't have Gleason. Newcombe didn't give a good match, same for Peterson. No milky sap.
Returned a few days later and worked it through in Voss to Macleaya, with a good match there and in google images - it is an escapee from cultivation. But supposed to have yellow sap. Not supposed to be a strong invader, but this colony of dozens of large individuals is doing well.