This looks like False Oxslip, Primula veris x vulgaris, a hybrid between, for example, a Cowslip and Primrose.
Although the wood satisfies the clay soil and dappled shade needed by the rarer true Oxlip, Primula elatior, it seems unlikely this is an example, given distribution patterns.
Picture taken March 20.
If you can confirm identification, please leave a comment below.
