Primroses grow mostly under trees and start flowering in March, before the new leaves of deciduous trees develop.
This is the very first primrose of this year, a common Cowslip (Primula veris) with small, dark yellow flowers. It grew all alone in a very grey and brown chestnut-wood, and it looked quite out of place and out of season.
Often you find primroses in larger groups, as here. You notice some dark yellow Cowslips and a lot of pale Common Primroses (Primula vulgaris). 
The flowers of the Common Primrose are larger and have shorter and less upright stems.All primroses have clear green, cockled leaves.
Intermediate forms between the two species are quite common. Here you see one.