Grey Belt Assessment – Advice Note
1. Background
1.1. The December 2024 NPPF sets out the new concept of grey belt. Annex 2 of the NPPF defines grey belt as follows:
For the purposes of plan-making and decision-making, ‘grey belt’ is defined as land in the Green Belt comprising previously developed land and/or any other land that, in either case, does not strongly contribute to any of purposes (a), (b), or (d) in paragraph 143. ‘Grey belt’ excludes land where the application of the policies relating to the areas or assets in footnote 7 (other than Green Belt) would provide a strong reason for refusing or restricting development.
1.2. Paragraph 143 of the NPPF sets out the Green Belt purposes as:
a) to check the unrestricted sprawl of large built-up areas;
b) to prevent neighbouring towns merging into one another;
c) to assist in safeguarding the countryside from encroachment;
d) to preserve the setting and special character of historic towns; and
e) to assist in urban regeneration, by encouraging the recycling of derelict and other urban land.
1.3. The advice note sets out guidance on how Development Management officers can consider whether an application site meets the definition of grey belt and/or whether development would ‘fundamentally undermine the purposes (taken together) of the remaining Green Belt across the area of the plan’, for the purposes of NPPF paragraph 155 criteria a).
1.4. This guidance applies the Practice Planning Guidance now set out in ID:64 and last updated on 27 February 2025 (“the Green Belt PPG”).
2. Spelthorne Green Belt Assessment
2.1. SBC undertook a Green Belt Assessment (GBA) Stage 1 in 2017 and Stage 2 in 2018 to assess the performance of Green Belt across the borough. The stage 1 GBA looked attwo tiers of Green Belt land – strategic Green Belt areas (‘Strategic Areas’) and local Green Belt areas (‘Local Areas’). The Strategic Areas are two broad areas identified through common landscape character, natural barriers, and their functional connections within the wider Metropolitan Green Belt. Local Areas form more granular parcels that were further assessed against the Framework’s purposes for their inclusion within the Green Belt.
2.2. The Stage 1 GBA split the Spelthorne Green Belt into 59 Local Areas and scored each against purposes a) to d).
2.3. Forpurpose a) to check the unrestricted sprawl of large built-up areas, the GBA1 considered the role of the Green Belt parcels in preventing the sprawl of London, but also in restricting the sprawl of large built-up areas across the Borough and within adjacent neighbouring local authorities. Two large built-up areas were identified in Spelthorne as follows:
· Staines-upon-Thames / Egham (Runnymede)
· Ashford / Sunbury-on-Thames / Stanwell
2.4. The NPPF does not provide a definition of ‘sprawl’ therefore the GBA adopted a simple definition, considering sprawl as ‘the outward spread of a large built-up area at its periphery in a sporadic, dispersed and irregular way’.
2.5. For purpose b) to prevent neighbouring towns merging into one another, the GBA stage 1 identified the settlements in Spelthorne and in neighbouring boroughs to determine gaps between settlements. This considered the gaps between all non-Green Belt settlements i.e. not just the boroughs main towns but also the smaller settlement areas.
2.6. Purpose c) to assist in safeguarding the countryside from encroachment, was assessed by considering openness and the extent to which the Green Belt can be characterised as countryside.
2.7. For purpose d) to preserve the setting and special character of historic towns, only Staines-upon-Thames conservation area was identified as potentially being impacted by this purpose, with Green Belt assessed in its contribution to the context and visual surroundings of historic town character.
2.8. The Stage 2 assessment went on to split the Local Areas identified at stage 1 into smaller sub areas. These were identified using a 250m buffer around each settlement and as such, not all Green Belt was assessed at stage 2. This finer grained assessment looked at the role of sub areas against the NPPF Green Belt purposes in a similar fashion to the stage 1 assessment and also considered how any change to Green Belt boundaries might affect the performance of the wider strategic Green Belt.
2.9. A stage 3 Green Belt assessment was undertaken in house by Spelthorne Borough Council in 2022. This report looked solely at the performance of sites identified for release from the Green Belt as allocations in the 2024-2039 Local Plan and drew largely on the stage 1 and 2 assessments.
2.10. The Green Belt Assessment studies are available on the Council's website at: Evidence Base - Spelthorne Takes Shape
3. Grey Belt Tests
3.1. The GBA studies have not been tested against the 2024 NPPF and updated PPG on Green Belt but nonetheless it provides a useful tool and foundation for assessing the performance of sites in the Green Belt and against the definition of Grey Belt.
3.2. To determine how up to date the GBAs remain in light of the updated policy and guidance, a review of the methodology has been undertaken by Strategic Planning officers against the 2024 NPPF and updated PPG on Green belt. That review informs the guidance set out below.
Step 1: Site Assessment Area
3.3. In determining how proposals in the Green Belt can be assessed and whether they are grey belt, paragraph 009 of the Green Belt PPG emphasizes the need to determine whether development of the site would fundamentally undermine the purposes of the remaining Green Belt, as opposed to any wider parcel of land that may have previously been assessed as part of Green Belt assessment work.
3.4. Furthermore, as the stage 2 assessment focused on land within a 250m buffer around each settlement, there is land within the Green Belt that was not previously assessed and will require assessment should it be subject to a planning application.
3.5. Individual sites will therefore need to be assessed against Green Belt purposes a), b) and d). The conclusions of any sub area from the GBA2, particularly where it was previously deemed to be strongly performing, will need to be reviewed in light of the updated guidance, namely the key differences set out below and the extent to which the development site comprises any previous assessment parcel.
3.6. Sufficient granularity in the areas of assessment will be necessary. Looking at smaller assessment areas, where appropriate, should ensure that opportunities presented by smaller parcels to accommodate development – such as those that are already developed or are well contained physically and visually - are not lost within overly large assessment areas/ parcels.
Step 2: Green Belt Purposes
3.7. The assessment of grey belt itself relates to purposes a), b) and d) only. Further guidance has been issued in relation to these[1]:
Purpose a) to check the unrestricted sprawl of large built-up areas
3.8. The focus of this purpose is on land adjacent to or near to a large built up area which “if developed, result in an incongruous pattern of development (such as an extended “finger” of development into the Green Belt)”.
3.9. “Sprawl” is a broad term that does not only cover buildings and development but the wider spread of the large built-up area and its urbanizing influences. Sprawl is defined as spread out over a large area in an untidy or irregular way[2].
3.10. To make a strong contribution to this purpose, a site will likely be at the edge of the large built-up area in that it can perform a role in containing development and in restricting sprawl. The presence of prominent features in reasonable proximity i.e. planting, topography, rivers, roads, railway lines etc. which might restrict the scale of outward growth, will weaken a site’s contribution to this purpose.
3.11. A site that makes a strong contribution to purpose a) will likely be free of development. Consideration will need to be given to whether development would result in an irregular pattern of development that would be at odds with the existing Green Belt form.
3.12. When identifying grey belt, only sites that make a strong contribution will be excluded. The presence of existing development that either encloses or partially encloses the site, or the physical features will reduce a site’s contribution to this purpose. Judgment as to whether urbanising influences are present will have to made, with the list of the features that weaken the land’s contribution set out in PPG not exhaustive.
3.13. The criteria used for assessing purpose a) within the GBA studies is considered to be broadly in line with the PPG Green Belt guidance as at Paragraph: 005 Reference ID: 64-005-20250225. Particular attention should be paid to the specific role of the site rather than any wider sub area in checking sprawl of the built up area. This includes the strength of any existing boundary features, the relationship with any nearby built up area and also the likely shape and line of development and how this may alter the existing pattern of the Green Belt.
3.14. When assessing performance against this purpose, a site’s relationship with built-up areas, both in Spelthorne and within adjacent boroughs, will need to be assessed. Appendix A provides a map of large built up areas identified through the GBA stage 1. This is still considered to be applicable in light of the updated Green Belt guidance and identifies the broad settlement areas present. When identifying large built-up areas, it is important to take into account wider patterns of development and not just towns, but how settlements relate to one another.
3.15. Appendix A shows that functionally, Stanwell, Ashford and Sunbury form one continuous large built-up area with minimal gaps in development present. Similarly, Staines upon Thames forms a large built-up area with Egham in neighbouring Runnymede to the west. Shepperton is not considered to form a large built-up area given its more compact and isolated nature, holding a limited relationship with other nearby settlements.
Purpose b) to prevent neighbouring towns merging into one another
3.16. The Green Belt PPG is clear that this purpose relates to the merging of towns, not villages or smaller settlements. The Spelthorne GBA2 focused on all settlement types under the assessment of purpose 2 and therefore this element of the assessment is now somewhat out of date.
3.17. When assessing this purpose, it is important to identify what constitutes a town and how extensive this is considered to be. Spelthorne does not have identified settlement boundaries therefore a combination of the following have been used to identify the extent of the borough’s towns:
· Ward boundaries
· Local Plan Policies map
· Key physical features e.g. roads or railway lines
3.18. Given the somewhat patchwork nature of Green Belt in Spelthorne and absence of settlement boundaries, there is a degree of ambiguity as to what can clearly be defined as within a town area or boundary, with villages and towns often separated by small areas of Green Belt. Similarly, there are also several instances of small developed urban areas which fall outside of the main town areas but are separated by Green Belt. It is therefore important to define boundaries and ascertain a site’s relationship with the town itself. This will help to determine how any adjacent potential development sites perform against purpose b).
3.19. Appendix B provides a map of towns in Spelthorne based on the above. This should be used to identify the town boundaries, although it is recognised that there will be instances at the micro scale where settlement patterns and local characteristics will need to be analysed in more detail to determine whether an area forms part of a town or not.
3.20. The site allocations identified for release from the Green Belt in the Spelthorne Local Plan 2024-2039 are included on the map to help assess the impact on nearby and adjacent green belt boundaries and the strength of its performance in relation to the potential new town boundaries.
3.21. Guidance on purpose b) sets out that to be strongly performing, a site is likely to be free of existing development, form a substantial gap between towns and development would likely result in the loss of visual separation of towns. Larger parcels are therefore more likely to make a strong contribution to purpose b). Smaller parcels that could be developed without the loss of visual separation between towns, or those that do not make a contribution to visual separation are deemed to be moderate or weakly performing respectively.
3.22. Visual separation is a key element of this purpose, as an illustrative feature of moderately performing parcels is that they are able to be developed without the loss of visual separation between towns. This could be (but is not limited to) “the presence or close proximity of structures, natural landscape elements or topography that preserve visual separation”.
3.23. Whilst the overall principles of the criteria used in the GBA to assess purpose b) are considered to be broadly in line with the PPG guidance on assessing this purpose, i.e. the size of the gap and the degree of visual separation between towns, the settlement size differs. As such, the GBA may be used as a starting point but careful consideration should be given to the size of the settlement adjacent to any proposed development site and where this is a village/smaller settlement rather than a town, the site will not be excluded from the definition of grey belt.
Purpose d) to preserve the setting and special character of historic towns
3.24. Again, this purpose relates to towns only, not villages and smaller settlements. The Spelthorne GBA1 identified “Staines-upon-Thames defined in the Staines Conservation Area Preservation and Enhancement Proposals (1991) as the sole geographical area of potential relevance to this assessment. The north-western part of the conservation area is within the Green Belt which appears to have contributed to retaining the open character of this area”.
3.25. Whilst Staines-upon-Thames is not officially designated as a “historic town” by organisations such as Historic England and Historic Town Trust in the sense of a protected status it does contain a conservation area. The small contribution the conservation area makes to the overall size and character of the town would need to be considered. The contribution of Green Belt in Spelthorne to purpose d) through the GBA was deemed to be limited.
Step 3: Application of Footnote
7
3.26. Any land which falls within the designations under footnote 7 of the NPPF (excluding Green Belt) and which would form a strong reason for refusal cannot by definition be grey belt. In Spelthorne, these designations are:
· Sites of Special Scientific Interest
· SPA, SAC or Ramsar
· Local Green Space (emerging Local Plan)
· Areas at risk of flooding
· Conservation Areas
·
Scheduled Ancient Monuments
Nationally Listed Buildings/Structures (& curtilage)
3.27. Where there is conflict with national policy on habitats, heritage, flood risk etc. there must be a “strong reason” to refuse. The application of footnote 7 will be largely dependent on the characteristics of a site, the nature of a development and/or the potential for mitigation to enable a conclusion to be reached on whether there is a strong reason for refusing or restricting development.
3.28. It is notable that this step follows the assessment of Green Belt performance (as per step 2) as all Green Belt needs to be considered in the first instance. This allows the provisional identification of grey belt ahead of a more detailed analysis of proposals against the footnote 7 designations as to not rule out land immediately from classification as grey belt.
Step 4: Identification of grey belt land
3.29. In accordance with the grey belt definition, such land comprises previously developed land and/or any other land that, in either case, does not strongly contribute to any of purposes a), b), or d) in paragraph 143 of the NPPF, 2024. It also excludes the land where the application of the policies relating to the areas or assets in footnote 7[3](other than Green Belt) would provide a strong reason for refusing or restricting development. Combining the conclusions from steps 2 and 3 will determine whether a site meets this definition of grey belt.
3.30. If a site is grey belt and fulfils all of the criteria of paragraph 155 of the NPPF, development is not regarded as inappropriate. This sets out that:
The development of homes, commercial and other development in the Green Belt should also not be regarded as inappropriate where all the following apply:
a. The development would utilise grey belt land and would not fundamentally undermine the purposes (taken together) of the remaining Green Belt across the area of the plan;
b. There is a demonstrable unmet need for the type of development proposed;
c. The development would be in a sustainable location, with particular reference to paragraphs 110 and 115 of this Framework; and
d. Where applicable the development proposed meets the ‘Golden Rules’ requirements set out in paragraphs 156-157 below.
3.31. In such a case, there is no need for very special circumstances under paragraph 153; it will have been determined (as above) that there is no strong reason for refusal under paragraph (d)(i) and footnote 7, and so if a proposed development complies with all the Golden Rules significant weight should be given in favour of the grant of permission, applying paragraph 158.
3.32. The PPG guidance on Green Belt however sets out that where grey belt is identified “it does not automatically follow that it should be allocated for development, released from the Green Belt or for development proposals to be approved in all circumstances…”. There are further steps to consider but a recognition of land as grey belt provides a gateway to considering whether development passes the appropriateness tests.
4. Appropriateness Tests
Impact on the remaining Green Belt
4.1. Consideration of the impact of development on the rest of the Green Belt applies not only to grey belt but all Green Belt.
4.2. The next stage is to consider the extent to which the release or development of grey belt land would fundamentally undermine the purposes (taken together) of the remaining Green Belt across the Plan area. This should not require a parcel by parcel assessment of the remaining Green Belt, as per the previous GBA studies but rather should consider whether release or development would affect the ability of remaining Green Belt from serving all purposes in a meaningful way.
4.3. The GBA2 undertook an assessment of the role of sub-areas as part of the wider strategic Green Belt parcels in which they are located. This considered whether release of a sub-area would impact the assessment of the remaining wider Green Belt performance. Given that the GBA stages 1 and 2 used different definitions of the Green Belt purposes to those more recently set out in guidance, it is considered that these conclusions cannot wholly be relied on, however the qualitative aspects of the previous GBAs may provide a useful foundation for assessing the wider impact. Further consideration should however be given to the specific impacts of development on the wider area.
4.4. This step should focus on the level and form of development proposed and its relationship with the wider Green Belt; any localised impacts anticipated and the degree to which any impacts can be mitigated. This step should also focus on the potential impact of cumulative development in the area and long-term protection of the wider Green Belt. Assessment of this criteria should be undertaken both at the micro scale and the macro scale i.e. the adjacent Green Belt land to any potential development site and the wider more strategic swathes of Green Belt within which the site may sit and impact upon respectively.
4.5. The maps within Appendix A and B will be helpful tools in assessing the likely impact on the wider Green Belt, particularly along with the cumulative impact of the Local Plan Green Belt release sites. There is also a need to consider any cumulative impacts resulting from the development of a number of sites in the same area.
4.6. Where sites have been identified for potential development, the resultant Green Belt boundary and whether it is permanent and recognisable will need to be considered. This will help to assess the degree to which the surrounding Green Belt will be impacted. This step should consider the performance of the Green Belt as a whole, rather than minor impacts on neighbouring parcels. This may be a relatively high bar to hit in a lot of circumstances.
Is there a demonstrable unmet need for the type of development proposed?
4.7. Paragraph 155 of the NPPF sets out that “The development of homes, commercial and other development in the Green Belt should also not be regarded as inappropriate where all the following apply…There is a demonstrable unmet need for the type of development proposed”.
4.8. For housing, a lack of five-year housing land supply or a Housing Delivery Test score of less than 75% equates to a ‘demonstrable unmet need’. There are no specific measures for other uses therefore a judgment based on available evidence will need to be made.
Would the development in the grey belt be in a sustainable location?
4.9. The NPPF is clear that promoting sustainable patterns of development is a key consideration in determining whether or not development proposed in the Green Belt would be inappropriate (paragraph 155). Paragraphs 110 and 115 should be key considerations when assessing sustainability of the location.
4.10. This step should be determined in light of local context and site or development specific considerations, including the type of development proposed. This step should consider opportunities to maximise sustainable transport solutions.
4.11. Spelthorne is a relatively compact borough and therefore most sites will be located within a reasonable distance to a settlement. To aid the assessment of this test however, a set of indicative criteria is set out below.
4.12. Sites within a 250m buffer around the urban area are considered to be the most sustainable. Where a site is not located within or immediately adjacent to a settlement, further assessment of its sustainability will be required. This may include its ability to provide new services on site, or nearby and its ability to improve local connectivity. A map setting out the 250m buffer zone around the urban area is provided in Appendix C.
4.13. In line with the NPPF, sites should be assessed to determine whether they facilitate and encourage the use of sustainable modes of transport. Accessibility plays a critical role in assessing the relationship of a site to the settlement, key facilities, services and employment areas.
4.14. Approaches to measure service accessibility by walking are inconsistent. Sustrans (2022)[4] carried out a study on walkable neighbourhoods by local authority and found that the distance from a service over which a site would be classified as ‘poor’ or ‘unacceptable’ ranged from 240m to 5km. Furthermore, National Design Guidance gives 800m as a distance most people are willing to walk, although people tolerate slightly longer distances for certain services. Overall the Sustrans study found 800m a standard walkable distance, and 1.6km the longest distance a majority of people are willing to walk to meet their daily needs. These thresholds should be used to assess the sustainability of location and access to services.
4.15. Walking distances to local services such as schools, health centres/GP surgeries, local convenience retail, bus stops or rail stations with good services should therefore be assessed. In addition, public transport access to major centres of employment/service centres should also be a factor in assessing residential development.
4.16. Employment sites should be assessed based on their accessibility for the local workforce. The safety and suitability of access arrangements will also be an important consideration in determining the sustainability of the location.
4.17. In addition to the more quantitative measures set out above, a qualitative appraisal should also form part of the assessment, considering local character and context, any planned future infrastructure (and its level of certainty), and any identified supporting measures that would improve the site’s sustainability.
4.18. Where grey belt land is not in a location that is or can be made sustainable, development on this land is inappropriate.
Golden Rules
4.19. Where major development involving the provision of housing in the Green Belt is proposed, the ‘Golden Rule’ contributions should be made, as set out in paragraph 156 of the NPPF, 2024. These relate to affordable housing, infrastructure improvements and green spaces.
5. Impact on openness
5.1. Footnote 55 to the NPPF sets out that if development is considered to be not inappropriate development on previously developed land or grey belt, then this is excluded from the policy requirement to give substantial weight to any harm to the Green Belt, including to its openness.
5.2. This is consistent with rulings from the courts on these matters that, where development (of any kind, now including development on grey belt or previously developed land) is not considered to be inappropriate in the Green Belt, it follows that the test of impacts to openness or to Green Belt purposes are addressed and that therefore a proposal does not have to be justified by “very special circumstances”. See Appendix D on Grey Belt case law for further detail.
Figure 2: When is development in the Green Belt not inappropriate under paragraph 155 of the NPPF? (PPG Green Belt, Paragraph: 010 Reference ID: 64-010-20250225)
