Clematis: Anybody know what this is?, 1 by fancyvan

fancyvan wrote:
This is quite an old clematis rescued from a home near me before it was knocked down. The current owner thought it had a purple flower which around here would mean a Jackmani. However last year and this year it produced a flower or two and it certainly is not purple. I actually dug it up 3-4 years ago and this are the first flowers.
It really is a beauty and I am wondering if anybody can put a name to it?