This experiment studied the effects of sheep grazing a formerly fertilized lowland neutral grassland near Oxford in southern England at different intensities and times of year on sheep production, the flora and invertebrates. The aim was to identify regimes that enhanced species-richness while also supporting average levels of sheep production. Grazing in either winter or spring increased the number of plant species the following summer and autumn. However the soil seed bank largely consisted of species common in the sward or of weeds from adjacent arable crops, so diversification requires an external seed source. Sward heights were monitored weekly in summer and sheep numbers adjusted to achieve either high (6 cm) or low (3 cm) target sward heights. There were generally more invertebrates in paddocks grazed to a target sward height of 6cm rather than 3 cm in summer, but not as many as in adjacent, ungrazed grassland. Target sward heights took longer to achieve and swards were more heterogeneous when grazing had not occurred in the previous season. Sward surface height measurements are a potentially useful tool for linking nature conservation and livestock management. In this experiment sheep weights in summer and autumn were higher when swards were grazed in either the previous winter or spring.