Professor Ian McDonald, one of the world’s leading neurologists, made an unparalleled contribution to the understanding of multiple sclerosis and the management of people affected by it.

He was also a world authority on nervous system diseases that affect the eye.

At the time of his death he was Emeritus Professor of Clinical Neurology at the Institute of Neurology at University College in London. He was also Consultant Physician Emeritus at the National Hospital for Neurology and Neurosurgery, Queen Square (London), one of the leading centres for academic and clinical neurology in the world.

Over his distinguished career Professor McDonald received a raft of international honours and in 2000 was given an honorary Doctor of Science from the University of Otago, where he studied in the 1950s.

Though his career was played out on a world stage he always considered himself a New Zealander and visited regularly, most often while his elderly mother, who lived in Wellington then Feilding, was alive.

Professor McDonald was born in Wellington but the family moved to Christchurch where his father, William McDonald, managed an insurance business.

The young Ian was educated at St Andrew's College. As a schoolboy he wrote an essay on the topic of the nervous system of the earthworm. Years later, when he was a famous authority on nervous systems of a higher order, he told the story at lunch to an elderly Queen Mother. She snapped at him: "I didn't know they had one."

His first degree was a Bachelor of Medical Science in neurophysiology from Otago and, after finishing his medical training, he returned to the physiology department to complete a PhD.

He applied the techniques of neurophysiology to the study of multiple sclerosis and in his PhD showed that the loss of myelin, the insulating sheath around human nerves, caused slowing and blocking of nerve impulses. Later, at Queen Square, he showed myelin, the loss of which is the basic abnormality in multiple sclerosis, could be reformed, offering hope for multiple sclerosis sufferers.

He was, at Otago, taught by Professor Archie Macintyre and Dr Keith McLeod. He was a brilliant student, an engaging conversationalist and a clever mimic with a good line in deflating pomposity. Then and later he disliked sport, preferring to pretend he had no idea who the All Blacks were playing. he loved walking and music, and at one time he aspired to be a concert pianist.

Much later in London he helped young New Zealand musicians, including Michael Houstoun and Richard Mapp, find their feet. In London he rounded his life with cultural pursuits shared with his partner, Stanley Hamilton, reading and cooking.

But his work was his focus. He had not been dextrous enough to consider surgery but he was a brilliant diagnostician. While he was a house surgeon he recognised and published work on a very rare condition, giving himself an entry to London. He was a consultant physician at Queen Square from 1966-98 and was appointed professor of clinical neurology there in 1974 and head of the department of neurology in 1995. From 1969-96 he was consultant physician (neurologist) at Moorfields Eye Hospital in London. He undertook many visiting professorships, gave named lectures and gave time to many professional and university bodies.

He served as president of the World Congress of Neurology, the European Neurological Society and the Association of British Neurologists. He was a scientific adviser to the National MS Society (USA) and chairman of the MS International Federation’s Medical Advisory Board. From 1991-97 he was editor of Brain magazine.

He was a leader in the field of multiple sclerosis, making important contributions in the areas of genetics, physiology and most recently imaging. With the support of Britain’s Multiple Sclerosis Society he pioneered the use of magnetic resonance imaging in improving diagnosis and understanding of the disease.