Atypical meningioma is a tumour that arises from the lining of the brain. It mostly affects adults, with most patients in the 40-60 year age group. The primary treatment for atypical meningioma is surgical removal, but with surgery alone up to 40% of patients will experience recurrence. Because of this risk, some clinicians give early radiotherapy, whilst others advise regular monitoring with radiotherapy given only at recurrence. Currently there is no consensus as to which of these two approaches is best. This randomised controlled trial will compare the two approaches, and aims to determine whether early radiotherapy reduces the risk of tumour recurrence compared to regular monitoring in newly diagnosed atypical meningioma.