I had an early introduction to these as I attended Great Bardfield primary school and my uniform sweatshirt was emblazoned with one.
Great Bardfield drew Henry Doubleday's attention in 1842 when he described the 2 acre meadow of Bardfield Hall "as a mass of yellow blooms" with Oxslips (Primula elatior) growing by the thousand. On careful observation he felt they were probably a separate species from the False Oxslip ( now known to be Primula vulgaris x primula veris = P. x polyantha ) which was widespread in England at the time. He carried out cross pollination experiments, and the plants always bred true, so as a further check he sent plants to Charles Darwin who did the same and also crossed Primroses and Cowslips. Darwin's results were set out in a paper published in 1868 and left him in no doubt that the plants from Bardfield represented a separate true species which he referred to as the Bardfield Oxslip - now Primula elatior
Bardfield Oxslips - now more often known as just Oxslips, have a fairly limited distribution in the UK and are mostly confined to the boulder clay of the Suffolk/Essex border. They are commoner on the continent, where they are also often found in woodland glades.
The other parent, the Cowslip - also known as Peggles in Essex. ( P. veris)
And a couple of other Primrose hybrids also found at Abbeycwmhir.