 The primary efficacy measure will be the change in the ESRS dyskinesia score from baseline to endpoint. This will be analysed using analysis of covariance, including baseline score, treatment received, the centre and the centre-by-treatment interaction as factors. Comparisons will be performed by intention-to-treat, with last observation carried forward LOCF. An additional analysis will be performed on the per-protocol population, and an analysis will be performed on the per-protocol population without the LOCF to assess the effects of any withdrawals from this trial. 