Policies are constructs.  Case law establishes what the wording of a policy means or implies.
For example: what is a valued landscape?  How is this assessed and what kind of value does it relate to? Also how does green belt relate to openness? And what is the relevance of setting for heritage assets etc?

Landscape Value
Landscapes do not have to be designated to be valued – a landscape may be valued by someone who likes to walk their dog in it.  However, a valued landscape has to have attributes which make it out of the ordinary and be more than just somewhere you walk your dog.  The ‘Guidelines for Landscape and Visual Assessment’ (Third Edition) describes the factors that establish landscape value in Box 5.1.  This shows that it is not just landscape quality and condition but can also include other factors such as rarity and association. This can also include perceptual qualities such as tranquility and other experiential features.  Value is commensurate with statutory designation, but a non-designated area can also be within a valued landscape.

Versus Green Belt Openness
A greenbelt’s purpose relates to its openness and permanence; the prevention of coalescence; and the preservation and enhancement of the landscape setting of historic towns.  But openness is not defined.  It does not relate to visibility, although it contains a visual element but rather the absence of development.  Openness may not equate to visual impact.

The Issue of Setting
There is a visual dimension to the preservation of the setting of a heritage asset.  However, setting is not strictly defined in only visual terms and there does not have to be an inter-visibility between elements for there to be a historical relationship which is deemed significant.  The National Planning Policy Framework (NPPF) states that the setting relates to the ‘surroundings in which a heritage asset is experienced’. Therefore, the perceptual qualities of a setting including noise and smell may also have some relevance (e.g. tranquility in the setting of a religious shrine).   The NPPF also states, “extent is not fixed, and this may change as the asset and its surroundings evolve”.
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Case law matters because it answers the question posed by loose policy wording.  

Source:
NPPF Seminar, LI Seminar 21.02.2019 - Paul Brown QC, Landmark Chambers – What’s Law Got to do with it? The Future of Landscape Led Planning Under the NPPF

Net Gain relates to an approach to development and land management that aims to leave our natural environment in a measurably better situation than before development took place.  Net gain can include positive outcomes for biodiversity or natural capital or environmental net gains for the natural environment.  This will lead to better designed and considered ‘place making’ and is not intended to inhibit built development but provide better development that relates to its surroundings.
Net gain can be on site or where there is insufficient space there can be strategic offsetting or tariff payment or a combination of approaches.  Conservation of existing assets is not enough to prevent habitat loss. A policy of providing a network of inter-connected sites with stepping stones and green corridors between will establish a more resilient and adaptive environment.

​It is important to have a mechanism in place for measurement.  The DEFRA metric utilizes a mitigation hierarchy: avoid (this is the preferred option); mitigate; or compensate.  Many developers such as Berkeley, Redrow and Millwood are already voluntarily incorporating Net Gain into their proposals.
Appropriate assessment is essential: if there is no evidence of what is on site beforehand, there will be no evidence of a negative or positive impact following development. As Peter Drucker stated, “What gets measured, gets managed”.
Trading rules are built in.  There is a requirement for a ‘like for like’ replacement and improvement.  A 10% increase is suggested but not mandated.  It is down to individual local authorities to decide.  Some authorities are aiming high and setting the net gain requirement at 20%.
There is a business case for incorporating Net Gain into development proposals.  Measuring and responding to what is on site reduces risk and produces viable masterplans that respond to each specific location individually.  It also enables effective cost control and potential improved income.  Incorporating biodiversity does not have to be expensive.  Using native species and mowing regimes to encourage wildflower meadows can be cost effective.

The Government consultation on whether net gain should be mandated closed on the 10th February.  The consultation related to whether Net Gain should apply to all development under Town and Country Planning excepting permitted development and whether Net Gain should be mandatory.
A new DEFRA metric 2.0 will be launched in the spring.  This will include:

• Green infrastructure;
• Rivers;
• Intertidal; and
• New connectivity multipliers.

This could later be extended to marine planning.  This will be freely available and will included detailed guidance and a free user tool.
An ECO metric is currently being tested on a phased two year programme using data from Balfour Beatty and Highways England among others.  This will be a bolt on to the DEFRA Biodiversity Metric and will look at providing a wider environmental Net Gain approach: encompassing clean air and water.; mitigating and adapting to climate change; sustainability and reduction of waste; and managing exposure to environmental hazards.

Source:
NPPF Seminar, LI Seminar 21.02.2019 -Nick White , Natural England – Net Gain: From Emerging Concept Towards Mainstream Reality