The National Health Service Act of 1946 laid the foundations for a free and comprehensive health service.

After long campaigns by left-wingers and health workers to modernise Britain's system of voluntary hospitals and local authority services, the NHS came into being in 1948.

The principle of a health service "free at the point of delivery" was first advocated by the Beveridge report of 1942. The influential treatise recommended a universal system of comprehensive social insurance, which could provide sickness, maternity and unemployment cover, "from the cradle to the grave."

Sir William Beveridge, an economist, civil servant, and later a Liberal MP, sold more than 600,000 copies of his report, which established the framework for the Welfare State.

Clement Attlee's post-war Labour government introduced the NHS Act after deft negotiations between Aneurin "Nye" Bevan, the minister for health and housing, and private doctors, many of whom opposed the creation of the NHS. As a compromise, doctors were allowed to continue in private practice if they chose to do so.

Mr Bevan resigned from the government in 1951, after Herbert Morrison and Hugh Gaitskell introduced prescription charges, which he believed undermined the principle of a completely free service.

A decade later, a huge hospital-building programme was begun. Diseases such as diphtheria and tuberculosis were effectively wiped out and, as life expectancy increased, Britain's NHS was held to be "the envy of the world."

But longer lives led to rising costs. In 1989-1990 Margaret Thatcher undertook a huge overhaul of the NHS, and was heavily criticised by unions and Labour politicians for effectively privatising parts of the service, particularly its administration.

The "internal market" she introduced was scrapped by Tony Blair, who made the NHS a top political priority in the 1997 general election. He introduced a 10-year plan to uphold the basic principle of a health service free at the point of delivery, while focusing resources on tackling specific illnesses such as cancer and heart disease.

But in an attempt to cut waiting lists and improve standards, Mr Blair allowed the private sector to play a limited role. He signed a "concordat" which would allow the NHS to use private beds and private nursing homes.