| 1948 | Practice established by John J. Meldrum |
| 1975 | Practice name changed to Meldrum & Mantell with H. J. L. Mantell, Dip Arch, RIBA, FRIAS becoming a partner |
| 1987 | John J. Meldrum retires from practice |
| 1998 | H. J. L. Mantell gained RIAS Accreditation: Level 3 |
| 2003 | H. J. L. Mantell has RIAS Accreditation renewed at Level 4. |
| 2003 | Assistant Architect Michael Ritchie gains MSc in Building Conservation Technology and Management from Herriot Watt University |
| 2004 | Michael Ritchie joins practice as partner. Name of firm changed to Mantell Ritchie |
| Civic Trust Special Mention | - | 1992 |
| Aberdeenshire Council Design Award Highly Commended for Conservation on Banff Castle | - | 2004 |
| Aberdeenshire Council Design Award Commended for Conservation work on Banff Aisle | - | 2004 |
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