Perry was born in Dundee, son of Fletcher and Flora Perry, and educated at Ayr Academy, and the High School of Dundee. He studied medicine at St Andrews University earning his MB ChB in 1943, his MD in 1948 and a DSc in 1958. Between 1944 and 1946 he worked as a Medical Officer in Nigeria. He later worked as a scientist for institutions like the Medical Research Council. In particular he became an expert on polio. He had a reputation for following the scientific method rigorously.
He developed his career at Edinburgh University as Professor of Pharmacology, later Dean of Medicine and Vice Principal. In 1969 he became Vice Chancellor of the Open University and made that university into an effective institution proving that sceptics had been wrong. He was mainly responsible for deciding that the Open University would not compromise on academic standards - he was determined that its qualifications should be of equal academic value to non-distance learning Universities. Walter Perry worked further to develop distance learning through the United Nations.
He entered the House of Lords being created a life peer with the title Baron Perry of Walton, of Walton in the County of Buckinghamshire on 9 February 1979, later taking the SDP and Liberal Democrat whips, and served on the committee dealing with science and technology. He kept working right up to his death in 2003.
A collection of Walter Perry's papers, containing work relating to the Open University, other distance education institutions and work for the House of Lords, are preserved in the Open University Archive
- Kelly, J. S.; Horlock, J. H. (2004). "Walter Laing Macdonald Perry KT OBE, Baron Perry of Walton. 21 June 1921 - 17 July 2003: Elected F.R.S. 1985". Biographical Memoirs of Fellows of the Royal Society. 50: 201–225. doi:10.1098/rsbm.2004.0015. PMID 15768488.
- The London Gazette: . 1 January 1957.
- The London Gazette: . 13 December 1974.
- The London Gazette: . 13 February 1979.