Dr. Marshall reports grants from Bart's Charity, during the conduct of the study; personal fees from GE Healthcare, personal fees from Biogen, grants from NIHR, grants from Innovate UK, grants from Tom and Sheila Springer Charity, grants from Michael J Fox Foundation, outside the submitted work. Dr. Noyce reports personal fees from Britannia Pharmaceuticals, grants from Parkinson's UK, grants from Barts and the London Charity, personal fees from Profile, personal fees from Neurology Academy, grants from Virgina Keiley Benefaction, personal fees from Roche, personal fees from Biogen, personal fees from LEK consulting, personal fees from AbbVie, personal fees from BIAL, grants from Aligning Science Across Parkinson's & MJFF, personal fees from Movement Disorders Society, personal fees from UCB, outside the submitted work. Dr. Neligan has nothing to disclose. Dr. Dobson reports grants from Barts Charity, grants from MS Society of Great Britain, grants from Horne Family Charitable Trust, grants and personal fees from Merck, personal fees from Roche, grants and personal fees from Biogen, personal fees from Teva, personal fees from Sanofi Genzyne, grants from Celgene, personal fees from Janssen, outside the submitted work.