Hexton Chalk Pit long since ceased to be used for that purpose and "has been colonised naturally by fine-leaved fescue grasses and chalk-loving plants as well as five species of orchid". I'm quoting the description given by the Herts and Middlesex Wildlife Trust who manage the site as a nature reserve. The Common Spotted Orchid (below) is indeed common here. The other four are the Fragrant Orchid, Pyramidal Orchid, Bee Orchid and Common Twayblade.