While Charles was away from Cambridge the couple wrote to one another frequently, and their letters are catalogued below. A sizeable majority is from Charles to Grig (680, against 300 from her to him), a discrepancy in numbers attributable to her keeping most (if not all) of his, whereas he (at least until the arrival of John) kept relatively few of hers.

His letters discuss his views on the progress of the war and his hopes and fears for the future of British archaeology; and describe life at Medmenham and Eastcote (and his lodgings in Marlow and Ruislip respectively), his horticultural activities in his mother’s garden at Reading, his keen interest in the flora and fauna of the neighbourhoods in which he found himself, and his experiences of flying bomb raids. Grig’s letters principally tell of life in wartime Cambridge, send news of relations and friends, and report in detail on John’s progress.