Regulatory change programmes are notorious for running past their original timeline, and the explanation offered afterward is almost always the same: the requirement was more complex than initially scoped. In my experience reviewing these programmes, the complexity was usually visible from the start — what changed was the firm's willingness to admit it during planning.
Initial scoping conversations happen under pressure to present a credible, board-approvable timeline, which creates a quiet incentive to underweight the genuinely uncertain parts of the requirement — the parts where the regulation is ambiguous, or where the firm's existing systems will need to be tested rather than assumed compliant. These uncertain elements get scoped optimistically, not because anyone is being dishonest, but because presenting genuine uncertainty at the outset is organisationally uncomfortable.
The programmes that hold their timeline are, consistently, the ones that scoped the ambiguous elements as ambiguous from day one — building explicit discovery phases for the parts of the requirement nobody could confidently interpret yet, rather than assuming a specific interpretation and discovering the error mid-programme.
This requires a different relationship with the sponsoring committee: presenting a timeline with genuine uncertainty ranges attached to specific phases, rather than a single confident date. It's a harder conversation to have upfront, and a considerably easier one to have overall, since it avoids the credibility cost of missing a confidently stated date later.
Most regulatory programmes don't run long because the regulation was harder than expected. They run long because the scoping conversation wasn't honest about what was genuinely unknown at the time — and that honesty, uncomfortable as it is, is the actual lever available to fix the pattern.