The aim of this study was to assess the consequences of feasible land-use change in Great Britain on GHG emissions mainly through the gain or loss of soil organic carbon. We use estimates of per-area changes in soil organic carbon (SOC) stocks and in greenhouse gas (GHG) emissions, coupled with Great Britain (GB) county-level scenarios of land-use change based on historical land-use patterns or feasible futures to estimate the impact of potential land-use change between agricultural land-uses. We consider transitions between cropland, temporary grassland (<5 yr under grass), permanent grass (>5 yr under grass) and forest. We show that reversion to historical land-use patterns as present in 1930 could result in GHG emission reductions of up to ca. 11 Mt CO2-eq./yr (relative to a 2004 baseline), because of an increased permanent grassland area. By contrast, cultivation of 20% of the current (2004) permanent grassland area for crop production could result in GHG emission increases of up to ca. 14 Mt CO2-eq./yr. We conclude that whilst change between agricultural land-uses (transitions between permanent and temporary grassland and cropland) in GB is likely to be a limited option for GHG mitigation, external factors such as agricultural product commodity markets could influence future land-use. Such agricultural land-use change in GB could have significant impacts on Land-use, Land-Use Change and Forestry (LULUCF) emissions, with relatively small changes in land-use (e.g. 5% plough out of grassland to cropland, or reversion of cropland to the grassland cover in Nitrate Vulnerable Zones of 1998) having an impact on GHG emissions of a similar order of magnitude as the current United Kingdom LULUCF sink. In terms of total UK GHG emissions, however, even the most extreme feasible land-use change scenarios account for ca. 2% of current national GHG emissions.