These are six Central line stations in the Epping Forest district of Essex (and two on the boundary) that are included in zones 4, 5 and 6; seven Metropolitan line stations in Hertfordshire and Buckinghamshire that are included in local ancillary zones 7, 8 and 9; three London Overground stations in Hertfordshire, included in local ancillary zones 7 and 8; and fourteen National Rail stations of other operators just outside Greater London that are included in zones 6 to 8.