Strachey ceased work as a full-time salaried employee of the N.R.D.C. in March 1959. From 1 June 1959 he entered into an Agreement with the Corporation to work for it as a private consultant for a specified number of days in each of the three years to 1962. The Agreement was renewed in May 1962 for a further six months, covering the period June-December 1962.

Some of the material in the working papers, notes and calculations series relates to commissions undertaken for N.R.D.C. under this Agreement; see especially work for Royal Radar Establishment, on Ship Fairings, Traffic Control and EMIDEC, and Strachey's tabulated chronicle of his activities in MS. Eng. misc. b. 283/D.103.