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The draft guidance emphasises the importance of understanding heritage significance as a process separate from preparing the scheme proposals or designing out harm to significance. While this sequence is important, it also recognises that as designs develop and investigation works are carried out, an asset’s significance may be better revealed or understanding of it may change. Understanding significance is not a linear process, but it should form an important baseline.
For Southbank Centre, a statement of significance and diagrams illustrating areas of importance formed key parts of the accessible conservation plan for the site.
The draft guidance also touches on the methodology used to assess significance: it identifies that while sensitivity matrices and scoring systems can be useful quantitative tools, ultimately “significance and impact are matters of qualitative and expert judgment”. Any quantitative methods should be used in conjunction with a narrative argument identifying what contributes to significance, why it matters and how the proposal would affect the asset’s significance.
Our statement of significance on West Horsley Place - a Grade I listed Tudor mansion - utilised both quantitative and qualitative methods of assessing the significance of the wider site.
As practitioners, we agree with paragraph 6 of the draft guidance, which highlights that it is crucial for significance to be identified up front to save abortive work and cost. However, it is difficult to define a proportionate scope of assessment without having an initial scheme in which to respond. The process needs to be iterative and may require a staged approach to understanding significance, with more detailed assessment of significance carried out on areas where alterations are proposed.
We note in paragraph 10 of the draft guidance that applicants are encouraged to agree the precise extent and nature of an assessment of significance with the local planning authority. While this is laudable best-practice, it is often unrealistic given the time constraints upon local planning authority conservation officers and difficulties getting in touch with them as a result. In addition, costs and time delays associated with pre-application consultation may mean that in practice, agreeing the scope of the assessment of significance with the conservation officer in advance may not always be practicable.
When Historic England (as English Heritage) published Conservation Principles in 2008, this was a milestone in a qualitative approach to heritage significance. It encourages the practitioner to consider why an asset is important and this thinking has been incorporated into the NPPF. However, the question of how to assess the scale of that significance (how important is the asset) has not been addressed in policy or guidance even though it is an essential consideration in the balancing process that is the planning system. This new guidance stresses the need to identify the level of significance but leaves such evaluation to expert judgement. Given the difficulty in codifying such a process for the whole range of asset types this may be the most sane approach to take.