Tizard was born in New Zealand but spent most of his professional life in England where, as a psychologist, he worked at the boundaries of psychology, medicine, education and the social sciences.

His work on alternatives to institutional care in the 1950s and 1960s underpinned the subsequent development of 'ordinary life' models for children and adults with learning disabilities.

After her death, John Tizard and his three children moved back to Timaru to live with the family of Jack's grandmother, Emma.

He was fortunate to have as a philosophy lecturer the renowned philosopher of logic and scientific method, Karl Popper, who had moved to New Zealand in 1937 after the Nazis came to power in his native Austria.

He spent five years in the field ambulance service in Greece, North Africa and Italy, as a medical orderly and stretcher bearer.

[7] Tizard's initial brief, together with his colleague Neil O'Connor, was to research the occupational potential of people with learning disabilities (then called 'mental deficiency' and later 'mental handicap', terms that are now outdated).

[6] During Tizard's undergraduate years he had also joined the university Socialist Society[1] and the power of Socialist ideas and policy were confirmed when the New Zealand government passed the Social Security Act 1938, covering unemployment benefit, pensions and universal health care, the first example in the world of comprehensive Welfare State provision.

Later, Tizard's former membership of the Communist Party caused him some problems in gaining visas to visit America, but because of his high reputation there these were eventually overcome.

In the mid-20th century, large numbers of people with learning disabilities were detained in institutions with little legal protection in the UK, under the 1913 Mental Deficiency Act.

[15] One of Tizard's major achievements was to link high quality scientific research to political agendas for change, particularly from a Socialist perspective.

[1][2][6][16] Tizard remained at the Social Psychiatry Research Unit from 1948 to 1964 when he was appointed professor of child development at the Institute of Education, University of London.

[22] If a book with that title had been published in the first half of the 20th century it would almost certainly have reflected the agenda of the Eugenics Movement:[23] the belief that social problems such as poverty, unemployment and criminality result from learning disabilities being inherited through families, and that the solution lies in programmes of sterilisation, incarceration or even extermination.

[1][2] Apart from the early promotion of workshops for training and employment of adults with learning disabilities,[20] the first model service set up and evaluated by Tizard was the Brooklands experiment, bugun in 1958.

The book pioneered the thinking that would lead eventually to the closure of nearly all institutional care for people with learning disabilities in the UK and their replacement with small-scale, developmentally oriented local services.

[35] In 1962 Tizard negotiated substantial long-term funding from the Department of Health for an ambitious project based on his research strategy.

A doctor with experience of epidemiology and care of people with learning disabilities, Albert Kushlick, was appointed to develop and lead this project, working from the Wessex Regional Hospital Board in Winchester.

[42] Professionally, the philosophy of 'normalisation', providing services that give people experiences as close as possible to those generally valued in ordinary society,[43] had gained much support in Scandinavia, the US, the UK and other countries.

[44] In parallel with the Wessex Project, Tizard had initiated and secured funding for a study of management practices in different kinds of residential provision for children, with a focus on those with learning disabilities.

In collaboration with the child psychiatrist Michael Rutter and a senior medical officer at the Department of Health, Kingsley Whitmore, Tizard had also initiated and negotiated funding for a major study of disability amongst a complete cohort of children aged 9 to 12 years on the Isle of Wight.

The collaborative project demonstrated another key feature of Tizard's research, the bringing together of different fields and disciplines in the study of social issues.

His brief was to develop research as well as teaching activities that would still have an emphasis on disability but would also offer opportunities for the study of wider issues affecting children.

[51] As well as continuing his involvement in the projects he had already initiated, during his time as professor at the Institute of Education Tizard widened his research interests.

[53] He expanded his advisory work and published articles on a wide range of topics[18] as well as overseeing many research projects carried out by colleagues and students.

In the early 1970s Tizard negotiated with the Department of Health for long-term funding of a unit dedicated solely to research projects that could be coordinated and would ensure the building up of multi-disciplinary expertise.

For example, in 1976 he gave a powerful rebuttal to the notion that services for young children and their families could and should be provided cheaply, at a conference with the title 'Low Cost Day Provision for Under Fives' organised by the Department of Health and Social Security.

[70] A clear rationale for this linkage was given in a report to the Chief Scientist at the Department of Health and Social Security in the year of Tizard's death.

[76] The high quality and pioneer nature of Tizard's research led to him being invited to join or contribute to many advisory and policy bodies.

This was in part because of the powerful charisma which he developed over the years; the qualities which contributed to this…included the exceptional warmth and generosity with which he responded to almost everyone he met, a steadiness of character and deep moral conviction combined with wit and high intelligence".

[1] His colleagues wrote of him: "In committee, as everywhere else, he showed courtesy, loyalty, total honesty and integrity, and combined these with continuous clarity of thought.

In wider fields, many went on to hold professorships and research posts at universities in education, psychology, psychiatry, sociology and criminology, studying a wide range of aspects of social policy, especially in relation to children.