This paper analyses the local lockdown measures introduced to contain the spread of Covid？19 in the UK. We use a spatial regression discontinuity design to assess whether the fall in business activity during the lockdowns was driven by the policy measures or by other factors, such as voluntary social distancing. We conclude that the local lockdowns did causally reduce business activity but that activity would have probably fallen substantially even in the absence of the lockdowns. During the local lockdowns, the average turnover growth for SMEs in the UK was around -20%. SMEs that were up to two kilometres inside the lockdown boundaries had 8 percentage points lower turnover growth than those up to two kilometres outside. This implies that the local lockdowns accounted for two fifths of the overall drop in business activity at most. The estimates are largest for restaurants and non-food retail (eg clothes shops), which were directly targeted by the restrictions. Costs fell by much less than turnover, reducing cash flow.