A British chemist who helped uncover the mechanism that powers living cells has been awarded the Copley Medal, believed to be the world's oldest scientific prize.
Professor Sir John Walker joins a long procession of illustrious scientists who have received the award from the Royal Society since 1731.
Among them are famous names such as Charles Darwin, Benjamin Franklin, Albert Einstein and Stephen Hawking.
The Copley Medal, which predates the Nobel Prize by 170 years, is the Royal Society's top honour and is awarded for outstanding achievement in scientific research.
Sir John carried out ground-breaking work on biological processes within the mitochondria, cellular power houses that generate energy. He is director of the Medical Research Council Mitochondrial Biology Unit in Cambridge.
The research earned Sir John a share of the Nobel Prize for chemistry in 1997.
His work focused on an enzyme called ATP synthase which plays a central role in producing a cell's energy "fuel".
Sir Paul Nurse, president of the Royal Society, said: "John's breakthrough work on ATP synthase has been absolutely fundamental to our understanding of what powers living cells and thereby all life.
"Without his contributions to our knowledge of the process by which nutrition is transformed into energy, many subsequent discoveries could not have been made."