This globally rare species of Dock is threatened throughout its world range. It is a perennial species of sand and shingle beaches, coastal rocks and damp dune-slacks. It requires a constant supply of fresh water so is usually found close to streams and springs. In Britain it has been recorded from the Scilly Isles (where it is now extinct), Devon and Cornwall, with outlier populations in Glamorgan and Anglesey. Elsewhere it is only known only from north-west Spain, north-west France and the Channel Islands. Throughout its world range many populations have been lost through the construction of costal sea defences. Natural processes including winter storms have also resulted in the loss of some populations. Our material is from Anglesey.