Read our May 2025 article: Understanding Heritage Impact Assessments for World Heritage Sites – A process, not just a report.
World Heritage in the spotlight
Over the past year, World Heritage Sites have remained firmly in the spotlight, shaped by sustained ambitions for economic growth and continued interest in securing UNESCO World Heritage inscription. In July 2026, 25 new sites were added to the World Heritage List. While none were in the UK, both the City of York and Birkenhead Park continue to progress their nomination processes.
Yet questions remain about how development, economic growth and change can be balanced with the protection of a World Heritage Site’s Outstanding Universal Value (OUV).
Recently, both UNESCO and Historic England have cautioned the City of London, during consultation on their new draft Local Plan, that the cumulative impact of proposed tall building development could threaten the historic setting of the Tower of London World Heritage Site, or potentially put its status at risk.
In Bath, debates continue about the challenge of delivering Government housing growth targets in the context of a national housebuilding crisis, while retaining the city’s dual World Heritage inscription.
Against this backdrop, we revisit the Heritage Impact Assessment process and reflect on what the past year has taught us about balancing change with the protection of OUV, the cultural and/or natural significance, which is so exceptional as to transcend national boundaries and to be of common importance for present and future generations.[1]
A clearer policy framework for World Heritage Sites in England
In 2022, UNESCO published new guidance for assessing the impact of development on the OUV of World Heritage Sites through a Heritage Impact Assessment process. While developed outside the context of the UK planning system, many of its principles are now reflected within national policy.
While not explicitly referring to the UNESCO guidance, the new NPPF provides further detail and clarification for assessing the effects of development proposals on World Heritage Sites and draws on the approach and principles of that guidance.
For the first time, the NPPF chapter on the historic environment includes a specific decision-making policy for World Heritage Sites (HE8). There is also a combined plan-making policy for World Heritage Sites and Conservation Areas (HE2).
Policy HE8 introduces increased emphasis and nuance in relation to World Heritage Site impacts, perhaps reflecting the current scrutiny of perceived impacts of development pressures on a small number of high-profile UK World Heritage Sites in recent years by ICOMOS and others.
HE8 captures key principles from the UNESCO guidance while aligning with the established and updated framework for the consideration of effects to designated heritage assets, now at HE5 and HE6.
Significance and OUV: related but distinct
HE8 explicitly refers to a World Heritage Site having both significance and OUV. This provides welcome clarity and reflects the requirement of the UNESCO guidance to consider ‘other heritage and conservation values’ that a property may have in addition to OUV. This may include aspects of the place, which are of national or local significance and, while not sustaining OUV, are nevertheless of aesthetic, historic, scientific, social or other value. Such values should be considered separately and not conflated with values identified in a World Heritage Site’s Statement of OUV as adopted by the World Heritage Committee.
What the new NPPF means for development proposals affecting World Heritage Sites
NPPF Policy HE8 requires proposals to be designed in a way that "pays particular regard" to the significance and OUV of the World Heritage Site, including any contribution made by its setting, which may include a buffer zone, but may extend further.
This approach mirrors the Heritage Impact Assessment process set out in the UNESCO guidance, which requires an early approach to understanding OUV. It also aligns with Historic England's Good Practice Advice in Planning 2: Managing Significance in Decision-Taking in the Historic Environment, which advocates early assessment and understanding of significance and potential impacts.
Furthermore, HE8 requires proposals affecting World Heritage Sites to be supported by an assessment of impact on significance, attributes of OUV and any potential cumulative impacts that is informed by appropriate evidence, such as visual impact assessment. This reflects the UNESCO guidance requirements to assess ‘attributes[2]’ of OUV, cumulative effects and draw on multi-disciplinary evidence as appropriate to the characteristics of the specific World Heritage Site and the nature of the proposals.
The role of the World Heritage Site Management Plan is heightened through both HE2 and HE8. In plan-making, HE2(1)(b) requires that the relevant policies and objectives in World Heritage Site Management Plans should be taken into account. HE8 requires that development proposals have regard to the World Heritage Site Management Plan. We expect greater interest and scrutiny of Management Plans as a result, particularly in their preparation, as they are now explicitly tied to national planning policy.
HE8 establishes a clear and pragmatic framework for assessing development proposals affecting World Heritage Sites or their settings:
- Buildings and features that make a positive contribution should be retained, where possible.
- It is recognised that not all elements of a World Heritage Site will necessarily contribute to its significance or OUV.
- Where development proposals would result in the loss of a contributing building or other element, the relevant considerations are: a) the significance and contribution made to OUV by the element affected, and b) the contribution to the significance of the World Heritage Site as a whole.
- Effects should be assessed in accordance with Policies HE5 and HE6, which set out a framework for the consideration of harm where it occurs. This re-states the UK Government’s position that drawing a balance between the protection of significance and OUV of a World Heritage Site and wider public benefits is compatible with the World Heritage Convention (1972).
- Proposals that conserve those elements of a World Heritage Site or its setting that make a positive contribution or better reveal its significance, should be supported.
Earlier assessment, stronger evidence and better case-making
The direction of travel is clear. Assessment of the potential effects of development proposals on the significance and OUV of a World Heritage Site needs to happen earlier in the project lifecycle. Heritage Impact Assessments should be informed by multi-disciplinary evidence, and Management Plans are likely to carry more weight.
When executed effectively, Heritage Impact Assessment can demonstrate how change can proceed without undermining Outstanding Universal Value and find the right balance between optimising development and avoiding/minimising heritage impacts as a critical part of effective case-making.
Read our article, What the NPPF 2026 means for heritage decision making, for a broader overview of how the updated NPPF is shaping heritage policy and decision-making across England.
Our Heritage, Townscape and Landscape team has valuable experience and specialist expertise supporting clients and project teams through the Heritage Impact Assessment process to manage and reduce risk. Recent examples include:
• Bath Rugby Club, City of Bath / Great Spas of Europe World Heritage Sites
• Belper Mills, Derwent Valley Mills World Heritage Site
• Devonport House, Maritime Greenwich World Heritage Site
• The India Buildings and Cowgate, Edinburgh Old and New Towns World Heritage Site
For further information, please contact Kerrie Melrose.
2 November 2026
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[1] MHCLG (2026) NPPF: Annex B: Glossary
[2] Attributes are the elements of a heritage place that convey its values and make them understandable. They can be physical qualities, relating to the material fabric and other tangible features, but can also be intangible aspects such as processes, social arrangements or cultural practices, as well as associations and relationships which are reflected in physical elements of the property. (Guidance and Toolkit for Impact Assessments in a World Heritage Context, UNESCO, 2022)
