Five new teams will join the Stags in the Isthmian Division One South for the 2017-18 season.
Ashford United, Shoreham, Phoenix Sports, Thamesmead Town and VCD Athletic have been announced as the new additions by the FA, with no team from step three joining the league.
Tooting & Mitcham United and Dorking Wanderers both earned promotion last year, while Chatham Town, Three Bridges and Godalming Town all dropped to step five.
Ashford United, a phoenix club of Ashford Town (Kent), join as champions of the Southern Counties East Premier Division, while Shoreham finished finished top of the Southern Combination Premier Division last year after late drama. Initial champions Haywards Heath Town were deducted nine points a month after the season finale, resulting in Shoreham claiming the league title. The remaining sides all join from the Isthmian Division One North.
Local neighbours Molesey will provide the local derby once again as the Casuals return home to Waterside Drive, while a 190-mile round trip to Ramsgate’s Southwood Stadium will continue to prove the longest mainland journey for supporters.
Isthmian Division One South 2017-18
Ashford United, Carshalton Athletic, Chipstead, Corinthian-Casuals, Cray Wanderers, East Grinstead Town, Faversham Town, Greenwich Borough, Guernsey, Hastings United, Herne Bay, Horsham, Hythe Town, Lewes, Molesey, Phoenix Sports, Ramsgate, Shoreham, Sittingbourne, South Park, Thamesmead Town, VCD Athletic, Walton Casuals and Whyteleafe.