To the public, Francis Crick was one of the men who, with the American J. D. Watson, discovered the structure of DNA and received a Nobel prize for it. To his colleagues and students, he was one of the most distinguished and influential biologists of the 20th century, as well as one of the most flamboyant. Scientists would tell stories about Crick the way politicians once told stories about Churchill. This public image was not one that Crick wholeheartedly relished.

He had cultivated much of his persona to cut a dash in the world of microbiology, where his true worth was known; he did not much care that it provided so prominent a mark in the public eye. Yet Crick was an original, looking at the world in ways his colleagues could often hardly fathom.

Francis Harry Compton Crick was born in 1916 in Northampton, the son of Harry Crick. He was educated at Mill Hill School and University College, London, where he graduated in physics in 1937. He became a research student there, but before he could finish his work for a thesis the Second World War began and he became a member of the Admiralty’s mine design department.

During his time there he became aware that his real interests lay in biology rather than physics, and when he returned to civilian life in 1947 he decided to enter some field of biological research. He obtained a research studentship from the Medical Research Council and joined the Strangeways Institute in Cambridge, which made a speciality of research in cell biology. Soon he realised that he wanted to work at a more fundamental level.

In 1949 he joined M. F. Perutz and J. C. Kendrew in the Cavendish Laboratory, becoming the third member of the newly founded Medical Research Council Unit which later developed into the Medical Research Council Laboratory of Molecular Biology. He remained a member of the staff of the council throughout the rest of his career.

His major discovery, made in 1953 in close collaboration with his American colleague J. D. Watson, and based on the experimental work of M. H. F. Wilkins, Rosalind Franklin and E. Chargaff, was the double-helical structure of deoxyribonucleic acid (DNA), the substance which, in almost every living cell, is the repository of the hereditary information that determines the characteristics of the organism.

Crick and Watson reasoned their way to the structure of DNA on only the barest of the evidence provided by others. They built models again and again. “The important thing is to ignore data, which complicates life,” James Watson wrote to Crick in 1954. The first piece of the puzzle fell obediently into place. Crick then proposed that there must be small molecular tags, each type of which read the appropriate codeword on a gene and carried one sort of amino acid to the site where the protein was being assembled.

The structure of DNA showed that it could carry long messages; it seemed that it would be neat if those messages described the chains of amino acids that form proteins, but it would take another eight years, a lot of false starts and the resources of most of the large biological laboratories in the world to begin the translation of the language in which the message was written.

Giving as it did an immediate insight into the way in which the information is stored and passed on from generation to generation, the discovery of the double-helix structure of DNA was immediately recognised as perhaps the most important single contribution of the century to fundamental biology, and it gave Crick and Watson an international reputation almost overnight. The significance of the work was later recognised by the award of the Nobel Prize for Medicine jointly to Crick, Watson and Wilkins in 1962, the annus mirabilis for molecular biologists, which saw five of them invited simultaneously to Stockholm to receive the same honour.

The structure of DNA was, however, only one of a whole series of major contributions to our understanding of the molecular basis of living organisms, made by Crick throughout his career. Earlier on he had worked in the field of the X-ray analysis of proteins, as a critic of existing methodologies and an originator of new theoretical approaches. After the DNA structure, he was responsible for the formulation of the so-called “central dogma” that biological information, stored in nucleic acids and passed on by their replication, is transformed into protein molecules, but that the reverse transformation never occurs.

He played a leading part in the work that led to the elucidation in detail of the genetic code by means of which biological information is recorded. He was largely responsible for several concepts underlying the understanding of the mechanism by which biological information is translated into protein molecules, especially the idea of a “messenger” carrying information from one part of the cell to another, and for the “adapter hypothesis” which explains the way in which specific protein molecules corresponding to that information are assembled. Both of these fundamental concepts were confirmed by experiment.

Later he became interested in problems of cell differentiation. It is a significant illustration of the rapid development of the field of molecular biology into more and more complex biological systems, a development in which Crick himself had played a leading part, that the division of the MRC Laboratory of which he was joint head (with S. Brenner) was in 1969 renamed the Division of Cell Biology, when only 20 years before he had abandoned the classical field of cell biology in favour of what then seemed a more fundamental approach.

Crick’s great power as a scientist would have manifested itself in whatever field he had chosen to work; it derived from an individual and characteristic intellectual style. He had an unusual capacity for concentrated thought, and he argued with clarity and ruthlessness. Interminable discussions with his colleagues were a major element in his method of work, and he impressed them as having more sheer intellectual ability than anyone else they had met.