The trial will compare the effect on disease control and immunosuppression treatment of adding simvastatin 80mg once daily, over a follow-up and treatment period of 2 years. Patients will be randomised in a 1:1 fashion to standard treatment with placebo or standard treatment with the addition of simvastatin (80mg daily). They will be followed at 3 months intervals for 2 years with a primary end point of mean reduction in corticosteroid dosage at the 12 month follow-up visit.