# From McKinsey deck to working software: where strategy consultancies fall short
> Strategy · By Adam Hadley · 2026-04-07
The largest consultancies sell brilliant strategy and then hand it off to systems integrators who deliver eighteen months later. There is a better way.
## The execution gap is where value dies
MIT's NANDA initiative found last summer that 95% of enterprise generative AI pilots delivered no measurable return on profit and loss, despite $30 to $40 billion of corporate spending. The study looked at 300 public deployments and interviewed 150 leaders. The pattern was not about model quality or talent. It was about what happens between the strategy slide and the production system.
That gap is not new. McKinsey's own research with the University of Oxford, covering more than 5,400 large IT projects, found that the average programme runs 45% over budget, 7% over schedule and delivers 56% less value than promised. BCG's work across 850 transformations puts the outright success rate at roughly 30%. Strategy, on its own, has an even worse conversion rate: McKinsey's longitudinal surveys suggest that around 71% of strategic programmes fail to execute as designed, and only 21% of executives in the 2024 to 2025 cohort thought their strategy was even sound to begin with, down from 35% fifteen years earlier.
The numbers describe a single phenomenon. Strategy consultancies are very good at producing decks that make executives confident about a direction. They are structurally unable to ship the thing the deck describes.
## The anatomy of a handoff
A typical engagement still looks like this. McKinsey, BCG or Bain produces a 90-slide deck with a clear recommendation. The executive sponsor agrees. The deck is handed to a systems integrator, usually Accenture, Capgemini, Deloitte or Infosys, for "implementation". Eighteen months and several million pounds later, something resembling the original recommendation goes live, with most of the interesting parts cut for "scope reasons".
Here is the process as it is actually experienced by the sponsor.
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Every arrow in that diagram is where value leaks. The strategy team does not know what is hard until they hand it over, so "simple" recommendations turn into three months of integration each. The build team is paid to deliver scope, not outcomes, so they ship the original SOW even when reality has moved on. And the economic incentive for both firms is to lengthen the engagement, not shorten it. A 12-month programme is more profitable than a 6-week one. Speed is not in anyone's compensation plan.
## Receipts
The public record is full of what happens when this model meets a hard deadline. TSB's 2018 migration from Lloyds systems to its Spanish parent Sabadell's Proteo4UK platform crashed on go-live, locked 1.9 million customers out of their accounts, cost the bank more than £370 million in direct costs and compensation, triggered a £48.65 million fine from the Financial Conduct Authority and the Prudential Regulation Authority, and caused 80,000 customers to switch away. Two data centres were never tested before cutover.
The Co-operative Bank cancelled its Infosys Finacle core banking replacement in 2013 after writing off £148 million in IT costs. The original budget was £184 million. The internal forecast at cancellation was £948 million. KPMG had warned the board. The board pressed on.
These are not outliers. They are what the McKinsey-plus-SI operating model produces when the environment stops being forgiving.
## The cost of the execution gap in one chart
The shape of the problem is easier to see as a rough budget anatomy. Numbers are indicative, drawn from the McKinsey or Oxford overrun data and typical SI engagement breakdowns.
```diagram
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Roughly a third of the budget goes on work that exists only because the strategy team and the build team are different organisations. That is the execution gap, priced.
## What we do differently
QuantSpark is one team across strategy, design, engineering and analytics. We work in four to six week increments and ship working software at the end of each one. The strategy gets pressure-tested against the constraints of actually building it, not against a slide. The things we recommend are the things we then build. The things we build are in production within weeks of the recommendation, not quarters.
The gap closes because the handoff does not exist.
```diagram
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This is not a new idea. Pivotal Labs, Thoughtworks and a handful of others have been running variations of it for twenty years. The combination of strategic depth, design quality and engineering speed in one small team is still rare, though, and it is exactly the shape that asset managers, retailers and PE portfolio companies need when they have to learn quickly, validate before committing, and put working software in front of users while the opportunity is still open.
The Gartner prediction that at least 30% of generative AI projects will be abandoned after proof of concept by the end of this year is not a technology problem. It is a delivery model problem. Large firms have spent 2024 and 2025 proving that a deck plus a systems integrator cannot close the distance to production fast enough to matter.
## When the traditional model still fits
If you have a settled strategy, a multi-year budget approved by the board, and a remit to roll the same system out to 40 countries, the MBB-plus-SI model is genuinely fit for purpose. Industrialised rollout is what the big firms are built for.
If, instead, you need to answer a question you have not answered before, with a working system rather than a business case, the operating model has to change. That is what we built QuantSpark to do.
## Sources
- Gartner, "Gartner Predicts 30% of Generative AI Projects Will Be Abandoned After Proof of Concept By End of 2025", July 2024. https://www.gartner.com/en/newsroom/press-releases/2024-07-29-gartner-predicts-30-percent-of-generative-ai-projects-will-be-abandoned-after-proof-of-concept-by-end-of-2025
- MIT NANDA, "The GenAI Divide: State of AI in Business 2025", reported in Fortune, August 2025. https://fortune.com/2025/08/18/mit-report-95-percent-generative-ai-pilots-at-companies-failing-cfo/
- BCG, "How CEOs Can Beat the Transformation Odds", 2024. https://www.bcg.com/publications/2024/how-ceos-can-beat-the-transformation-odds
- McKinsey and University of Oxford, "Delivering large-scale IT projects on time, on budget, and on value". https://www.mckinsey.com/capabilities/mckinsey-digital/our-insights/delivering-large-scale-it-projects-on-time-on-budget-and-on-value
- McKinsey, "How Strategy Champions win, from insight to strategy execution", 2024-2025. https://www.mckinsey.com/capabilities/strategy-and-corporate-finance/our-insights/how-strategy-champions-win
- Financial Conduct Authority and Prudential Regulation Authority, final notices on TSB Bank, December 2022, reported by Computer Weekly. https://www.computerweekly.com/news/252528519/TSB-hit-with-huge-fine-after-IT-migration-disaster
- Computer Weekly, "Co-operative Bank ditches core banking migration", 2013. https://www.computerweekly.com/news/2240204553/Co-operative-Bank-ditches-core-banking-migration
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