This small white clematis started blooming in the past few days in a place where I never planted one. I'm not sure what it is. Many years ago I had a Sweet Autumn in a distant part of the garden, but it died years ago. None of the abutting neighbours have one, and this clematis has no scent. There used to be a Paul Farges (aka Summer Snow) near this area but it was dug out a year or two ago and never bloomed this late. Any guesses on what this is?
Picture taken through the pantry window of the top of the arbour where it appeared - there are multiple clematises on the arbour so most of the foliage does not belong to this one:
A closer view of a sprig with leaves and flowers - the flowers seem to have 5 tepals: