Sussex 1 (1987–1993) The original Sussex 1 was a tier 8 league with promotion up to
London 3 South East and relegation down to
Sussex 2.
Sussex 1 (1993–1996) The creation of
National 5 South meant that Sussex 1 dropped from a tier 9 league to a tier 10 league for the years that National 5 South was active. Promotion and relegation continued to
London 3 South East and
Sussex 2 respectively.
Sussex 1 (1996–2000) The cancellation of
National 5 South at the end of the 1995–96 season meant that Sussex 1 reverted to being a tier 8 league. Promotion and relegation continued to
London 3 South East and
Sussex 2 respectively.
Sussex 1 (2000–2009) The introduction of
London 4 South East ahead of the 2000–01 season meant Sussex 1 dropped to become a tier 9 league with promotion to this new division. Relegation continued to
Sussex 2 (briefly two regional divisions) until that league was abolished at the end of the 2003–04 season.
Sussex 1 (2009–present) Sussex 1 remained a tier 9 league despite national restructuring by the
RFU. Promotion was to
London 3 South East (formerly London 4 South East) and relegation was to
Sussex Canterbury Jack Intermediate (Sussex 2) which was reintroduced for the 2010–11 season after an absence of six years. ==Promotion play-offs==