Between 1999 and 2003, ATO Architects was actively involved in the Branch Roll-Out for Diamond Bank Ltd. This began with the design of the Branch in Isolo, Lagos, which was relocated from a rented property on Osolo Way, and then the design of the Branch on Adeola Odeku Street, Victoria Island, which had an innovative barrel roof entrance held by a steel space frame. This concept was very well received by the viewing public. Following the success for the Adeola Odeku Branch, ATO Architects developed a Prototype design, which was built in several other parts of the country. This began a long relationship with Diamond Bank, which led to the development of branches in the following locations:

1. Abuja Branch
2. Abuja Branch Extension
3. Abakaliki Branch
4. Asaba Branch
5. Benin Branch, Edo State
6. Coker Branch
7. Cotonou Branch
8. Cash Office, Cotonou, Benin Republic
9.Enugu Branch
10.Idumota Branch
11.Ikeja Branch Development
12.Isolo Branch
13.Jos Branch – Pending
14.Matori Branch
15.Mussebo Benin Republic
16.Owerri Branch
17.Port Harcourt Branch
18.Umuahia Branch
19. Uyo – Pending
20. Victoria Island Branch
21. Warri Branch
22. Yenagoa – Pending
23. Office Refit at UAC Building, Abuja
24. Ikeja Branch
25. Zongo, Benin Republic
26. Project management in Akwa Ibom State