01 · The problem
Fourteen spreadsheets, three of them load-bearing, none of them agreeing. Every month-end became a reconciliation exercise nobody trusted and everybody dreaded.
02 · The spec
The spec sprint spent most of its time on the least glamorous part: what each number actually means. Once the definitions were agreed and written down, the software was almost obvious.
03 · The build
Four milestones, each one replacing a specific spreadsheet and its manual steps. The team kept working in the old way until each milestone was reviewed — so there was never a big-bang cutover to be frightened of.
04 · The outcome
One console, one set of numbers, and about thirty hours a week back. The client's own analysts now extend it.