In the lifecycle for a business case, what precedes the initial business case?

The development of a Business Case is often an iterative process. Before significant investment is made in creating the detailed Initial Business Case (often called the Outline Business Case or OBC), a preliminary assessment is required to ensure the proposed change is viable. This assessment is the Feasibility study (or Feasibility Assessment). A feasibility study quickly evaluates the proposed initiative to confirm it is technically possible, financially justifiable, and strategically aligned (Business Feasibility). The outcomes of this study determine whether it is worthwhile to proceed to the more detailed, full business case development. The other options (A, B, D) occur after the initial business case is approved and investment is committed.

(Reference: BCS Business Analysis Practice – Business Case Lifecycle)