Born in Hammesmith, the second son of George William Chibnall, bakery owner, and his wife Kate.
Educated at St Paul's School and gained an Exhibition to Clare College where he matriculated in 1912.
He began the Natural Sciences Tripos Part I but this was cut short by the advent of War.
He applied for a commission, and spent three years serving mainly in the Army Service Corps. In 1917 he applied to join the Royal Flying Corps and learned to fly in Cairo; he gained his wings in 1918.
In 1919 he was taken on by Professor H.B. Baker to do research for the newly instituted PhD at Imperial College, but he later switched to study the nitrogenous constituents of green leaves with Professor S.B. Schryver, whom he succeeded in 1929. He gained his PhD in 1921.
After a year's work at the Chelsea Physic Garden, he was awarded a travelling scholarship to the USA. He secured a place with the leading expert on plant proteins, T.B. Osborne, at the Connecticut Agricultural Experiment Station.
In 1924 he joined the laboratory of Jack Drummond at University College London. In 1929 Cibnall took over the Chair of Bichemistry at Imperial College. He was appointed the second Sir William Dunn Professor of Biochemistry at Cambridge University in 1943. He resigned in 1949 since he felt it was a role more suited to a medically qualified biochemist.
His notable students included Fred Sanger, who was a double winner of the Nobel Prize for Chemistry. After he was awarded a PhD in 1943 he joined Chibnall's lab. Chibnall suggested Sanger work on methods of identifying the terminal amino acid of Insulin. Chibnall then declined to have his name on Sanger's paper on the grounds that Sanger should get all the credit.
He married his cousin Helen Isabel Cicely Chibnall (known as Cicely) in 1931. Cicely died in 1936, giving birth to their second daughter.
In 1947 Chibnall married Marjorie McCallum Morgan, whom he had met after corresponding about one of his historical interests. They had a daughter and a son. Marjorie died in Sheffield on 23 June 2012, aged 96.
Chibnall died in Cambridge on 10 January 1988.