Valeriana tripteris!

We bought this plant at a plant sale in one of the open gardens we visit, some two years or so ago. Much to John's horror it has to be said, as he told me it was growing along the verges in our lane, which turned out to be true! And yes, it's a spreader. But it's also very lovely. I never checked but simply assumed it was indeed the common valerian. But I have started to doubt that. The leaves for one are not like valerian leaves are described in my various wildflower books. So I did a Google image search, and yes, that came back as valerian but the pictures shown on the search looked very much like this plant but not exactly the same. So I'm sharing 3 pictures of it  on my blog today in various views to see if anyone has a more satisfactory answer for me. And I'm pleased to say it has now been established this is valeriana tripteris.