Hi, thanks. I looked up lesser celandine on the tortoise table and it does look the same. I better get digging tomorrow then to get rid of it. 🙂I would say it's Ficaria Verna:
Ficaria verna - Wikipedia
en.m.wikipedia.org
The Wikipedia image is not all that convincing, but if you Google image search, you'll see some of the leaves, which made me confident enough to make this suggestion.