You're right! And it did have yellow buttercup-like flowers earlier this year. I initially thought it was a buttercup but was confused about the leaf shape, then after the flowers had gone I noticed something with creeping-buttercup-like leaves is growing through it. So I assumed I'd been mistaken and the flowers actually belonged to the other plant.
Thank you! (And DampGardenMan)
Should I get rid of it? It seems fairly self-contained at the moment. It's in a little shady wooded area - although I did spot some growing in my lawn which might be a concern. I've heard it's a voracious weed. I've enough of those, I don't want another taking hold of my garden because I didn't nip it in the bud.
I'm not an overly tidy gardener; my garden is meant to be wildlife friendly with the wooded area a little bit semi-wild, for the birds and bugs. At the same time I don't want an uncontrollable wilderness on my hands!
Posts
https://www.google.com/search?q=Oxalis+enneaphylla+'Rosea'&client=firefox-b&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjep4fZ4oDbAhVFkywKHZyQAOkQ_AUICigB&biw=1920&bih=943
It would have had yellow flowers earlier in the spring...March.
http://www.aphotoflora.com/d_ficaria_verna_subsp_verna_bulbiferous_celandine.html
is lesser celandine!
https://en.wikipedia.org/wiki/Ficaria_verna