Texas This category is for cryptographers associated with GCHQ (Government Communications Headquarters), United Kingdom. Pages in category "GCHQ cryptographers" The following 12 pages are in this category, out of 12 total. This list may not reflect recent changes. A Conel Hugh O'Donel AlexanderB Patricia BartleyC Peter Calvocoressi Joan Clarke Clifford Cocks Rozanne ColchesterE James H. EllisP Pamela PigeonT John TiltmanW Malcolm J. Williamson Shaun WylieY Leslie Yoxall