tomaths It is not compulsory but it is highly recommended in the following scenario:
- if your foundation is higher than 1.2m or 5 courses of block.
- if you do not intend to do DPC/German floor of your house before continuing with the ground floor block work, you can introduce a capping beam on top of the foundation walls.
From the look, you are not in a swampy area and your foundation is not up to 6 courses of block so it is not compulsory.
Due to topography of your land, you can introduce double wall in areas where the foundation wall is up to 6 blocks high.
More mortar and bricks to your project.