After leaving the army, Cocks went up to Hertford College, Oxford in 1959 to read for a bachelor's degree in geology.

He subsequently became a research student at Oxford in 1962, funded by the DSIR, and completed his doctoral thesis on Silurian brachiopods from Shropshire in 1965.

[4] Cocks joined the staff of the Natural History Museum, London as Scientific Officer in the department of palaeontology in September 1965.

In 2019, Cocks published a monograph on Llandovery brachiopods, synthesising much of his taxonomic work of the previous six decades.

[11] He was appointed an Officer of the Order of the British Empire (OBE) in the 1999 New Year Honours for services to palaeontology.