Time-dependent density functional theory (TDDFT) has become a well-established technique for modelling excited state properties in molecular systems, and has been implemented in several quantum-chemistry codes. An implementation of TDDFT in CASTEP [2] will give the UK electronic structure community an opportunity to address cutting-edge scientific problems in areas such as inorganic and organic photovoltaic materials, catalytic reactions at surfaces, light-emitting polymer materials for optical displays, and femtosecond laser chemistry. Including the use of hybrid functionals promises to address some of the limitations that have previously hindered the application of TDDFT to extended systems. [3,1,7]