Mystery plant

Is this a weed or a good ground cover, and what is it?

 

Yes it is a weed or wild flower and in spring it is a ground cover..but in summer it vanishes and goes dormant.
It loves damp shady places.
It looks like Ficaria verna subsp verna...common name Lesser celandine.

British Wild Plant: Ficaria verna ssp verna Lesser Celandine

 

Many thanks for the information. It does look pretty, pity it can be invasive.