The 2009-10 National League 1, previously known as National Division 2, is the first season of the third division of the English rugby union competitions since the professionalised format of the second division was introduced with widespread league changes made by the RFU. As the new second division would reduce teams from 16 to 12, there were plenty of new additions to National League 1, itself increasing from 14 to 16 teams, with Esher, Newbury, Manchester, Manchester and Sedgley Park all dropping down from the old National 1 while Nuneaton and London Scottish came up from the 2008–09 National Division Three North and 2008–09 National Division Three South respectively (these divisions themselves now renamed National League 2 North/South).