Peer review against a second opinion on a technical report
Access to the underlying model and measurement files usually decides whether a peer review or a fresh second opinion is the right commission on a contested report.
A peer review of a technical planning report checks somebody else's work against the method it claims to follow. A second opinion throws the work away and answers the question again. Both are defensible, they cost very different amounts, and the choice is usually settled by one practical fact: whether you can get hold of the underlying model, measurement files and spreadsheets. Without those, a peer review is a reading exercise with a professional letterhead on it.
What each exercise sets out to do
A peer reviewer takes the report, the inputs and the working files, and tests four things. Whether the method matches the standard the report cites. Whether the inputs are the right ones for the site and the date. Whether the calculations reproduce. Whether the conclusions follow from the results. The output is a review note listing agreed points, queries and disagreements, usually with a recommendation on what would resolve each.
A second opinion starts from the brief rather than the report. The new author builds their own baseline, runs their own assessment and reaches their own conclusion, which may agree or disagree with the first. The output is a standalone report that can be submitted, relied on and defended.
The distinction matters most when the question is contested. A peer review can tell you that an acoustic assessment used the wrong reference time interval under BS 4142. It cannot tell you what the rating level actually is, because that needs new measurement.
Cost and time compared
A peer review of a single discipline report is normally a matter of days rather than weeks, and the fee reflects reading time plus a proportion of the original assessment effort. A second opinion costs something close to the original commission, sometimes more, because the second author inherits none of the survey work.
Then there are the hidden costs. A second opinion on anything seasonal, an ecology survey, a parking survey under the Lambeth methodology, a traffic count in a neutral month, is limited by the calendar rather than the budget. A Parking Survey commissioned in late July will not produce usable data, and no fee level fixes that.
Against that, a peer review can end up costing more overall if it identifies a flaw serious enough to require reassessment anyway. Scoping the review to the questions that actually matter, rather than asking for a general audit, is what keeps that from happening.
Access to the underlying data usually decides it
This is the practical test. Ask what the review would need.
- Acoustics: the measurement files with time histories, the calibration records, the survey log and the source data used in the calculation.
- Transport: the trip rate query and its site selection, the junction model files, and the survey data behind any local counts.
- Daylight: the three-dimensional model with the surrounding context, the room-use assumptions and the reflectance values applied.
- Biodiversity net gain: the completed statutory metric file, not a summary table, plus the habitat survey data and the condition assessment sheets.
- Contaminated land: the borehole logs, the laboratory certificates and the chain of custody records.
Where the original author will release those files, a peer review is efficient and proportionate. Where they will not, because the relationship has broken down or because the model is treated as their intellectual property, you are choosing between a review that cannot verify anything and a fresh assessment. Take the fresh assessment and say why.
Where a second opinion is the honest route
Four situations where a review is the wrong tool.
- The original assessment is out of date. Superseded climate change allowances, a revised metric version or a survey outside its accepted currency cannot be reviewed into validity.
- The dispute is about the baseline rather than the arithmetic. If the argument is whether a habitat parcel is modified grassland or other neutral grassland, somebody has to go and look.
- The original author has a position to defend. A review of their own work, or of work they scoped, is worth less to a decision-maker than an independent assessment.
- The report will be tested at an inquiry. An expert who has to give evidence needs to own the assessment, not comment on someone else's.
Disclosure when a review criticises your own report
This is the part people get wrong, and it deserves plain treatment.
There is no general duty to volunteer to a local planning authority a review that undermines your own submitted evidence. There is a duty not to mislead. The professional codes are consistent on this: the RTPI Code of Professional Conduct requires members to act with competence, honesty and integrity, and the RICS practice statement for surveyors acting as expert witnesses makes the expert's duty to the tribunal override their duty to the client.
So continuing to rely on a conclusion you have been told in writing is wrong is the thing to avoid. The practical responses are to correct the report, to withdraw reliance on the disputed conclusion, or to submit the corrected assessment. Sitting on an adverse review and pressing the original conclusion at an inquiry is where careers get damaged.
At inquiry the position tightens further. Expert witnesses are expected to set out any material qualification to their opinion, and an adverse peer review of their own work is a material qualification. If you commissioned the review, assume the other side may ask whether one exists.
Using a review at appeal
A peer review can be submitted with an appeal statement, and it carries the weight an inspector gives to a professional opinion on method. It is not evidence of the underlying facts. Two consequences follow.
The reviewer may need to appear. A review note from a named professional who does not attend a hearing or inquiry is easier for the other side to dismiss than a witness who can be asked questions.
And a review that only lists queries rarely moves an inspector. What moves an inspector is a review that says which conclusions are unsafe and what the correct answer probably is. If your reviewer cannot say the second part, you have discovered that you needed a second opinion.
The professional directory is the route for arranging independent review of a draft, and what competent person means in planning legislation covers the statutory competence rules that sit behind these choices.
Choosing on a contested application
A rough decision sequence that holds up in practice.
If the working files are available, the report is current, and the disagreement is about method, commission a scoped peer review naming the specific questions. If any of those three fails, commission a second opinion. If the matter is heading to an inquiry and the report is central to the case, commission a second opinion regardless, because your witness has to own it.
One honest uncertainty: there is no settled tariff for what a reviewer should charge or how long a review should take, and the range in the market is wide. Ask for a fixed fee against a written scope with named questions, and ask what happens to the fee if the review concludes that reassessment is needed. Also check whether the survey is still valid before you pay for either exercise.
PlanScope drafts the report structure and flags where facts are missing, and a reviewer from the directory can sign it off. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance rather than legal advice, so check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
What is the difference between a peer review and a second opinion?
A peer review tests an existing report against the standard it cites, using the original author's inputs and working files, and produces a review note. A second opinion starts from the brief, builds its own baseline and produces a standalone report that can be submitted and defended. One checks the answer, the other supplies a new one.
Do I have to tell the council about a review that criticises my own report?
There is no general duty to volunteer it, but there is a duty not to mislead. Continuing to rely on a conclusion you have been told in writing is wrong is the risk. The usual responses are to correct the report, withdraw reliance on the disputed conclusion, or submit a revised assessment before the decision is taken.
Which files does a reviewer need to do the job properly?
Whatever the calculation actually ran on. Acoustic measurement time histories and calibration records, junction model files and the trip rate query, the three-dimensional daylight model with context, the completed statutory biodiversity metric file rather than a summary, borehole logs and laboratory certificates. Without them a review cannot verify anything and becomes a reading exercise.
Can a peer review be used as evidence at appeal?
It can be submitted and an inspector will weigh it as professional opinion on method, though it is not evidence of the underlying facts. Reviews that only list queries rarely shift a decision. Reviews that say which conclusions are unsafe and what the likely correct answer is carry more weight, particularly if the reviewer attends.
When is a peer review the wrong tool entirely?
When the original assessment is out of date, when the dispute is about the baseline rather than the arithmetic, when the reviewer would be reviewing work they scoped themselves, or when the report is central to an inquiry case. An expert giving evidence needs to own the assessment rather than comment on someone else's.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.