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The landmark case of Hillside Parks Ltd vs Eryri National Park in 2022 has caused a shakeup in the legal world.

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This article was produced by Claire Petricca-Riding from Irwin Mitchell.

Welsh planning applications are normally determined by the local planning authority. Although, Welsh Ministers can determine the applications themselves in some cases. In the Hillside Parks case, it was Merioneth County Council who granted the original planning permission in 1967. This permission was for 401 homes to be built at Balkan Hill, near Aberdyfi, Gwynedd.

Last year, The UK Supreme Court handed down the judgement that Hillside Parks Ltd can’t rely on the permission granted in 1967.

Since 1967, only 41 of the intended 401 houses have been built. None of them are in accordance with the original plans. Over the years, several other plans have been granted at the same site, with all but two being implemented. Hillside Parks Ltd, the current owner of the site, brought action against Eryri National Park, Penrhyndeudraeth. They claimed the original scheme was still valid, so development could continue.

The Supreme Court ruled that developments made since the original scheme was granted made it “physically impossible” for the original plans to go ahead. The Supreme Court reaffirmed the ‘Pilkington principle’. This states that a planning permission doesn’t authorise development if and when the land is altered to the point of it becoming impossible to carry out the development.

Wales’s ‘plan-led’ system, which was reinforced by the Planning (Wales) Act 2015, allows some planning applications to be made to Welsh Ministers instead of local planning authorities. It also makes the appeal system more transparent.

The ruling from the Supreme Court caused a shake-up as it’s left the door open for lawyers to argue that permission could allow for parts to be severable.

The ruling also means potential hurdles for sites where development is already underway and where regular redesigns and new planning is needed. For such large-scale plans, flexibility is needed. However, this flexibility could be lost because of incidents like the Hillside case.

As a Partner in the Irwin Mitchell Planning Team, I can see that newer applications may not run into this trouble as long as they are created with this in mind. However, sites with work already in progress could face problems. For new applications, we are looking to futureproof as best we can, ensure severability as best we can, building flexibility as best we can. It is more manageable because you are looking forwards. The biggest headaches are looking backwards.

The Supreme Court has more work to do in terms of defining the conditions around these types of cases. They haven’t considered all of the issues. I think the point at this stage is one has to recognise the risks involved in drafting conditions and permissions. This could mean that Wales's plan-led system may need to be revised.

You can listen to an Irwin Mitchell podcast on Hillside Parks Ltd vs Eryri National Park, Penrhyndeudraeth, which has some more detailed discussion of this case and it’s potential impact on planning in the region.


Published on
Last updated
18 July 2023