Complex sentence: The design of the Doughnut reflects new ways of working that GCHQ hoped to acquire after the end of the Cold War, with its design facilitating talking among staff, and between them and the Director of GCHQ and his subordinates.
Split into simpler sentences: The design of the Doughnut reflects new ways of working that GCHQ hoped to acquire after the end of the Cold War. The building is designed to facilitate talking among staff, and between them and the Director of GCHQ and his subordinates.