The Trwyn y Parc solution pipes on the Isle of Anglesey, Wales, UK are one of only three onshore Miocene fossil flora bearing sites. Here we revise the palynostratigraphy and present new palaeoclimate data for this geoheritage site. By comparison to palynological data from northern Europe the age has been refined from Miocene to Middle Miocene, possibly Langhian. This is confirmed by palaeoclimate reconstructions comparable to the German Middle Miocene, especially the Langhian after the Middle Miocene Climatic Optimum (MMCO). This new information not only confirms the regional importance of Trwyn y Parc, but shows it to be of national importance Our findings show that this Regionally Important Geodiversity Site (RIGs) is of national importance as it is the oldest onshore fossiliferous Neogene deposit in the UK. Based on this, and the unique fossil flora preserved at Trwyn y Parc, the site has significant geoheritage value and should be upgraded to Geological Conservation Review (GCR) status and subsequently protected as a Site of Special Scientific Interest (SSSI).