We found these 1-pinnate shiny green leaves with 7 pairs of pinnae growing in a ditch running alongside a country house. Looking in my new 4th edition Stace, there are two Cyrtomium species.We identified this plant as Cyrtomium falcatum based on the number of pinnae pairs.It is native to eastern Asia and is grown as a house plant here. Being hardier than most cultivated ferns, it can occasionally escape and become established in damp sheltered areas.Here it was found with two fellow members of the Buckler Fern Family (Dryopteridaceae), Male Fern Dryopteris filix-mas and  Hard Shield-fern Polystichum aculeatum