The principal areas of Timothy Comyn's practice include town and country planning, highways, environmental, local government, transport and works, compulsory purchase and compensation, parliamentary law, and judicial review in these fields. He appears regularly at public inquiries and in the Administrative Division of the High Court acting for appellants, local authorities and third parties.

He appears regularly at public inquiries, hearings and examinations and in the High Court / Planning Court acting for applicants, appellants, local authorities, statutory undertakers and third parties.