Oughtonhead Common. I have been reading 'Wild Flower Habitats of Hertfordshire' by Brian Sawford which was published back in 1990. He mentions this area several times noting that "Marshes fed with highly calcerous waters can support a great variety of wild flowers". 

 He also notes it is one of the county's few remnants of marsh on boulder clay and refers to its wet grassland, sedge beds and fen characteristics. I intend to return to Oughtonhead at regular intervals in the year ahead.