This series comprises correspondence sent to other members of the Bell and Richmond families but which was held alongside Charles and family's papers. The sub-series are as follows:
- CPT/6/1 - Letters to Hugh Bell and Florence Bell nee Olliffe from and about Mary Katharine Trevelyan nee Bell
- CPT/6/2 - Letters to Elsa Richmond nee Bell from Mary Katharine Trevelyan nee Bell
- CPT/6/3 - Letters to various Bell family members from Mary Katharine Trevelyan nee Bell
Further correspondence from members of the Bell family can be found in this collection at CPT/2/5, CPT/2/6 and CPT/2/7.