In March 1985, there were claims that Rolls-Royce was in the process of conducting licensing talks for HOTOL engine technology with American propulsion company Rocketdyne. In April 1985, Pattie wrote to Secretary of State for Defence Michael Heseltine to propose a two-year £3 million proof of concept study be performed under a public-private partnership arrangement, consisting of £1 million provided by the UK government and the remainder being financed by Rolls-Royce and BAe themselves. Pattie reasoned that the project would serve Britain's "strategic capability, and that tests of key technologies could foster international collaboration. According to aerospace publication Flight International, the support of the Ministry of Defense (MoD) was critical as the design of HOTOL's engine had been classified.