The Rosemanowes HDR project in the period 1983-1991 continued experiments in HDR reservoir creation at depths of up to 2500 m in Cornish granite. A viscous gel stimulation was followed by an extensive characterisation of the reservoir created, using a long period of continuous circulation. The possibility of manipulating the system to improve its performance was explored, using secondary stimulations, placement of proppants in joints entering the production well, production pressure control using downhole pumps, and sealing sections of the production well to by-pass ＇short-circuits＇. Proposals were made for a ＇multi-cell＇ reservoir design, connecting cells in parallel between injection and production wells. The work of the Rosemanowes team has been concentrated on HDR projects outside the UK since 1991.