The Building Blocks of Modernising Legacy Systems
Which way out of your legacy system?
Six questions, the government's own seven warning signs, and the ten-year cost of doing nothing, with the Treasury's optimism correction shown, not hidden. (3 minutes to complete).
Part 1 — The Route
Answer for one system, the one you'd least like to explain to the NAO.
Part 2 — The Condition
Recommended Route
This is a self-check against published indicators, not a formal risk assessment. The real framework scores likelihood and impact separately; a discovery exercise runs it properly.
Part 3 — The Cost
Doing nothing, 10 years
Today's run cost, every year for ten, discounted at the Green Book rate of 3.5%. Assumes it gets no worse, which it will.
This route, corrected
Before the optimism uplift: . The corrected figure is the one to plan with.
The optimism uplift
+200%The Green Book's upper bound for ICT projects — the required starting point, not a worst case.
Take the numbers with you
We'll email you this summary, the route, the indicator read and the three figures, ready to hand when the conversation about this system finally happens.
Done — it'll be with you shortly.
Why we tripled the estimate
The Green Book instructs appraisers to start ICT projects at a 200% optimism uplift and reduce it only as the causes of overrun are mitigated: an evidenced business case, understood technology, tested assumptions, reaching the 10% floor by contract award. Answering six questions on a website mitigates none of them. Therefore, the honest default is the full uplift.
This is not a theoretical multiplier. HMRC's Securing Our Technical Future went from £312m to £437m; the NAO has reported legacy programmes at several times their original estimate. Any tool showing you an ICT estimate without this correction is showing you the number that gets business cases bounced.
The uplift comes down through work, not through waiting: every contributory factor on the Treasury's list is brought down by discovery (scoping, evidencing, de-risking), done before anyone commits capital. That is the point of doing it first.
What a discovery would settle
The defaults above are honest, but they are defaults. A short discovery exercise replaces them with your figures, and buys the uplift down from 200% to something a spending review will accept. That is the difference between a business case that survives and one that doesn't.
Talk to Certes about a discovery