With a few exceptions, most of the items in the collection date from 1961 - 1971, the last ten years of Sir Leonard's career.
The most notable feature of the collection is Item 4, the manuscript diary kept by Sir Leonard while Director of Engineering, Ministry of Supply, Department of Atomic Energy Production. Sir Leonard's daily entries from 4 Feburary 1946 until 30 August 1947 provide a valuable record of the early days of the UKAEA.
Most of the collection is business and industrial correspondence. The letters have been sorted into categories which reflect the various facets of Sir Leonard's activities and interests, both professional and social.