🏠︎ | Past Sessions | M&A Lessons Learned Open and Honest Insight Into Everything That Can Go Wrong in an Acquisition
- Event: Finance Forum 25
- Date: 7 October 2025
- Speakers: Donald Ewing, Head of Commercial Finance, National Gas
- Estimated read time: 6-7 minutes
Quick summary
This session explored why value is often lost after the deal is signed, not during negotiation.
Drawing on experience across more than 20 acquisitions, Donald Ewing focused on the practical realities that derail integrations, from over confidence in synergy models to cultural misalignment and weak ownership once the transaction completes.
The central message was clear. M&A failure is rarely about spreadsheets. It is about governance, behaviour, clarity of accountability, and whether finance stays engaged as a decision partner once the deal moves from paper to practice.
Why most M&A risk sits beyond the transaction
The discussion challenged a common assumption in acquisitions, that the hardest work happens before completion. According to Ewing, that mindset is itself a risk.
While financial modelling and due diligence are essential, they often create a false sense of certainty. Assumptions harden into expectations, and once the deal completes, attention shifts too quickly to the next priority.
The session framed this as a structural problem. M&A teams are often disbanded at the point where risk actually increases. Integration, culture, and delivery discipline then fall to teams that did not shape the original deal logic.
For finance leaders, this creates a gap between what was promised and what is realistically achievable.
The danger of optimism bias in acquisition modelling
One of the most consistent failure patterns discussed was optimism bias. Synergies look compelling on paper, but depend on behaviours, timing, and execution that are rarely stress tested.
Ewing described how synergy models often assume cooperation, speed, and alignment without explicitly planning for friction. In practice, integration creates uncertainty, distraction, and competing incentives.
This is where finance can unintentionally contribute to failure. If assumptions are presented as outcomes rather than scenarios, the organisation treats variance as underperformance rather than reality.
The session reinforced the importance of framing models as decision tools, not promises.
Culture is not soft risk, it is execution risk
Cultural misalignment featured heavily in the discussion. Not as an abstract concern, but as a direct driver of missed value.
Acquisitions bring together different ways of working, different risk tolerances, and different interpretations of success. Without explicit attention, these differences surface as slow decisions, duplicated effort, and disengagement.
Ewing stressed that culture shows up in everyday behaviours, how quickly issues are escalated, how comfortable teams are challenging assumptions, and how decisions are actually made.
When these behaviours are misaligned, even well designed integration plans struggle to land.
Governance gaps appear after the deal closes
Another recurring issue was ownership. During transactions, roles are clear and tightly managed. After completion, accountability often becomes blurred.
Who owns delivery of synergies. Who resolves trade offs between integration and business as usual. Who has authority when priorities conflict.
Without clear answers, decisions drift and value leaks quietly rather than through visible failure.
The session positioned strong post deal governance as one of the most underinvested elements of M&A, despite its outsized impact on outcomes.
The role of finance after completion
A key theme was the role finance should play once the acquisition moves into execution.
Rather than stepping back once the deal is done, finance leaders were encouraged to stay actively involved as translators and challengers. That means tracking leading indicators, not just lagging financial results, and surfacing issues early rather than explaining variance later.
Ewing framed finance as the connective tissue between strategy and delivery. When finance remains engaged, the organisation is more likely to course correct before problems harden into write offs.
“The deal doesn’t fail on day one. It fails slowly when no one owns the gaps.” Donald Ewing, Head of Commercial Finance, National Gas
What good looks like, practical actions for finance leaders
This session translated into several concrete actions for finance leaders involved in mergers and acquisitions.
Questions to ask before signing
- Which assumptions depend on behaviour change rather than process change
- Where have we allowed optimism to replace evidence
- What would have to go wrong for this deal to miss its objectives
- Who owns delivery once the transaction completes
- How will we know early if integration is drifting off track
- Whether decision making slows or becomes more centralised
- Whether synergy delivery is owned or treated as background activity
- Whether teams escalate issues early or work around them quietly
- Whether integration milestones are tracked operationally, not just financially
- Whether finance is invited into delivery conversations, not only reporting cycles
- Treating the financial model as a promise rather than a scenario
- Disbanding the deal team too early
- Assuming culture will align naturally over time
- Measuring success only through headline synergies
- Allowing governance to weaken once the deal closes
What good looks like in practice
Successful acquisitions treat integration as a programme, not an afterthought. They maintain clear ownership, keep finance embedded in decision making, and treat early signals as opportunities to adjust rather than evidence of failure.
In those environments, finance moves from scorekeeper to strategic partner, helping leaders make better decisions as reality diverges from plan.
Conclusion, M&A success is a leadership discipline
The session’s most valuable insight was that M&A failure is rarely dramatic. It is incremental.
Value erodes through small delays, unchallenged assumptions, and unclear ownership. Avoiding that outcome requires discipline after the deal, not just rigour before it.
For finance leaders, the opportunity is clear. Stay involved, stay curious, and treat acquisitions as living strategies rather than static transactions. That is where long term value is either protected or lost.
Key takeaways
- Most acquisition risk emerges after the deal completes, not before
- Optimism bias in modelling can obscure execution realities
- Cultural misalignment directly affects decision speed and delivery
- Weak post deal governance allows value to leak quietly
- Finance adds most value when it remains embedded in execution
Speakers
Head of Commercial Finance, National Gas, Senior finance leader with over 20 years’ experience across regulated and non regulated sectors, with extensive hands on involvement in acquisitions and integration delivery.