Is this Buttercup?

Is this Buttercup?

Observation - Is this Buttercup? - UK and Ireland. Description: Clumps of leaves up to ten inches high(including stems). Smaller leaves in uncurling bundles. Three leaves at the top of each stem and each leaf divided into three - but not completely. The edges of the leaves are wavy, some (as with this leaf) with the t

Clumps of leaves up to ten inches high(including stems). Smaller leaves in uncurling bundles. Three leaves at the top of each stem and each leaf divided into three - but not completely. The edges of the leaves are wavy, some (as with this leaf) with the tips of the waves rounded, some a bit more pointy.
Pale and dark blotches on leaves, the darker ones adjacent to the pale ones and very specially noticeable at first glance. The blotches occur at the divides /semi-divides / the lower bits of ins-and-outs.
My first thought was that these are buttercup leaves but don't remember seeing dark blotches like this before.