William Lumsden Walker was born on 17 July 1919 and died on 7 April 2005. It is an honour to celebrate his life and the impact of his vision, inspiration and friendship on so many people. In one lifetime, he was a humanitarian relief worker, a pioneer of modern community-based approaches to caring for people with a learning disability, a founder of present-day child and adolescent forensic mental health services and a world leader of the emerging specialty of child and adolescent psychiatry.

Dr Walker grew up and was educated in Aberdeen. After gaining MB, ChB in 1941, he worked in Aberdeen, Chester and Birmingham before joining the British Red Cross. He was sent to Holland and Germany to run hospitals for civilians and refugees at the end of the Second World War. There he met Riet Mallens from Tilburg, Holland, and they were married in 1948.

On returning to Britain, he worked in public health in Bristol before moving to Devon and specialising in psychiatry. He returned to Bristol for his first consultant appointment and became Medical Superintendent of Hortham Colony. He instigated many changes there that revolutionised the treatment of people with ‘mental deficiency’ and withstood criticism from the media and an inquiry, in which he was entirely vindicated, for his visionary leadership. He was awarded MD by Aberdeen University in 1963. After 11 years, he moved in 1966 to the Bristol Royal Hospital for Sick Children and remained there until his retirement in 1984. He was elected to a Foundation Fellowship of the Royal College of Psychiatrists in 1971. Subsequently, he was elected Chair of the, then, Specialist Section of Child and Adolescent Psychiatry at the Royal College of Psychiatrists and served from 1979 to 1981.

This slim biography does less than justice to Dr Walker and the impact that he had on all who came into contact with him. He was a doctor of prominent humanitarian values that sustained him throughout his life and he had a clear vision of what being a good doctor and psychiatrist meant. His life story bears this out. He engaged equally well, and equally, with his colleagues in psychiatry and other specialties, and particularly with the children who were his patients. He was called ‘Lumsden’ or ‘Lummy’ by all.

All who know him have their anecdotes. I remember him telling a story about one young man in the Kingswood secure unit who accused him of being a creep. ‘ Yes’, said Lummy, ‘I am and it's got me a long way. Perhaps you should try it; I can teach you’. The young man had intended his comment to be a scathing insult designed to ward off painful insights from a visitor from a different walk of life. Instead, the young man found his words accepted, deflected and used as a therapeutic dart that surprised him and gained his attention.

I recall, not long after we started working together in 1980, Lummy coming under weighty fire from one of the other professions in a multidisciplinary team meeting because he represented a discipline that stood accused of being deeply reactionary. ‘Right wing’, he said with a twinkle in his eye, ‘I am about as far left in medicine as you can go’.

It was the combination of Lummy's warmth, modesty, disavowal of worldly props, approachability and vision that made him a really great man. It was his ability to communicate with patients, staff and colleagues alike, and his leadership and openness to new ideas that made him such a fine doctor and teacher. It was his ability to stand aside and reflect, combined with his relentless hard work and concern for the most disadvantaged young people and families, and his humour that made him the excellent psychiatrist that he was. Lummy was my mentor and role model and a friend who made a truly enormous impact on me and on so many others. Truly, there are many people who owe an enormous amount to his life.