What a Former Client Would Change: The Due Diligence Question Most Buyers Skip

Most buyers treat a consultancy reference as a courtesy call at the end of a selection process. The proposal has been read, the interviews have been held, and the preferred supplier has been chosen. The reference call is then squeezed into a diary and conducted with the same rigour as a verbal confirmation that the firm is, on the whole, perfectly nice.

That is a missed opportunity. A reference call is one of the few chances to hear about the work as it was actually delivered, rather than as it was written up. A case study is a shop window. It shows the finished display, the tidy outcome and the client quote approved by a marketing department. A reference call can show the stockroom: the delays, the disagreements, the invoice that arrived larger than expected, and the moment when the project nearly came off the rails.

The point is not to hunt for scandal. It is to understand where friction is likely to arise and whether the consultancy has the temperament and discipline to manage it. In UK buying teams, where procurement often has to justify a decision to a finance director or a board, that understanding is worth more than another polished PDF.

The case study is not the evidence it appears to be

Case studies are not dishonest. They are edited. They tend to start after the messy beginning has been resolved and end before the benefits are fully tested. They rarely mention the change request that added 15 per cent to the budget, the partner who appeared at the kick-off and then vanished, or the data migration that took twice as long as planned.

None of those things necessarily make a consultancy a poor choice. Complex work involves friction. The question is whether the supplier recognises friction early, prices it transparently and manages it without turning every conversation into a commercial negotiation.

That is why the best reference questions are not about satisfaction. They are about behaviour under pressure.

Prepare the call as you would an interview

Before picking up the phone, ask the consultancy for more than one referee. Ideally, speak to the person who sponsored the work and the person who managed it day to day. They will often give different accounts. Ask whether the account manager can be absent from the call. A reference who speaks freely without a supplier listening in is more likely to tell you what you need to hear.

Have the proposal beside you. Know the promised scope, the fee structure, the named team and the timeline. Then use the call to test the gap between the promise and the delivery.

Questions that surface the real story

The most useful question is not whether the client was happy. It is what they would change. That single question often moves a reference from a polite endorsement to a specific account of the engagement.

Useful prompts include:

• What was the first sign that the engagement was going off track, and how was it handled?
• When the scope changed, how was the change priced and documented? Can you give an example?
• What did the final invoice include that you had not anticipated at the outset?
• Which part of the working relationship required the most management effort from your side?
• How did the consultancy behave when you challenged a recommendation?
• Who actually did the work, and how often was the partner involved after the pitch?
• If you ran the project again, what would you write into the contract that was not there the first time?
• For what kind of work would you not re-appoint them?

That last question is more revealing than a simple request for a yes or no on re-appointment. Most referees will say they would work with a firm again. Fewer will explain the boundaries of that enthusiasm.

Listen for specifics. A referee who says the team was excellent but cannot recall a single detail is offering a weak signal. A referee who says the first month was difficult because the data was poorer than expected, but the consultancy escalated early and absorbed some of the additional effort, is offering something far more useful. That is evidence of how the firm behaves when the plan meets reality.

Weigh candour against polish

Candid references can feel less impressive than case studies. They include hesitations, caveats and the odd awkward pause. That is often a sign that you are hearing from a real client rather than a scripted advocate.

Do not expect perfection. Expect self-awareness. A good consultancy will have clients who can describe difficult moments because those moments were managed, not buried. A consultancy that can only offer glowing, frictionless references may be selecting referees carefully, or it may be failing to notice when clients are unhappy.

Cross-check what you hear against the proposal. If the pitch promised partner-led delivery, ask how many days the partner spent on the work. If it promised fixed-price certainty, ask how change requests were handled. If two references mention scope creep, that is not a reason to walk away automatically, but it is a reason to tighten the change control mechanism in the contract.

Make the reference shape the deal

A reference call should influence more than the evaluation score. It should influence the contract. If referees mention that governance meetings drifted, add a stage-gate schedule. If they mention that fees crept when requirements changed, agree a clear rate card and a written change process. If they mention that the day-to-day team was junior, name the people who will do the work and make substitution subject to approval.

This is where reference checks earn their keep. They turn vague assurances into specific protections. They also give the buying team a language for the first review meeting: we know that this is the point where projects like ours tend to become difficult, so let us agree now how we will handle it.

A reference call is not a box-ticking exercise. It is a short, structured conversation that can prevent a six-month problem. For UK buyers under pressure to move quickly, that is a sensible use of forty-five minutes.

Ask what went wrong. Ask what they would change. Then decide whether the consultancy has the honesty and discipline to manage the answer.