This proposal will explore the effect of elevated pressure on the behaviour of two important hydrogen peroxide solvates of the explosive CL-20. We will use neutron diffraction to investigate changes in hydrogen bonding as a function of pressure for both solvates; (ii) follow the structural evolution of the solvates as a function of pressure; (iii) investigate whether the solvates desolvate at elevated pressures, and (iv) explore whether new forms can be obtained at elevated pressures and if so whether they can be recovered to ambient conditions. The high-quality structural data that will be obtained, including the effects of pressure on hydrogen-bonding motifs, will provide insight into molecular energy transfer, detonation mechanisms and, particularly the sensitivities to initiation.