Formal evidence of stutter for University?

Formal evidence of stutter for University? I have stuttered for the past 10 years (not from birth). My university course currently has multiple modules where there is an assessed verbal presentation - marks will be awarded for clear, confident, and persuasive presentation skills. There are also multiple group presentations where marks will be shared between each member (I obviously do not want to impede other members grades). I am applying to university disability services for help and advice on this assessment. Perhaps they will allow the group to present without the large audience of students being present. However, I need to have formal evidence (they suggest doctors notes, etc.). I do not believe I have any formal evidence? My personal GP may have it noted, and I took speech therapy classes many years ago which might have been recorded/billed to the NHS. Of course, my family, all my friends, and connections to people in positions of authority/honour (bank manager, degree holding engineers) know about my stammer. For others who have been in this situation, what formal evidence did you provide? And what help/aid did you receive? ​