The controversy was finally resolved by the work of Ben Peach and John Horne whose 1907 paper on the subject remains a classic text.

[11] There is a car park and interpretation centre that explains the geology of the area and gives background to the Highlands Controversy, along with three waymarked trails that take visitors to points of interest across the site.

The site also hosts artworks such as 'The Globe' by Joe Smith and 'Pipeworm’ by Susheila Jamieson that were commissioned to highlight the inspiration that the landscape has had on artists and poets.

After further fieldwork, Nicol changed his mind and advocated instead that the contact at the base of the upper gneisses was tectonic, starting what was known as the Highlands Controversy.

The results of the mapping proved conclusively to Peach and Horne that the contact was tectonic and they were eventually able to persuade Geikie when he visited them briefly in the field in October 1884.

In 2004, following a review of all NNRs in Scotland, it was decided to remove NNR status from the wider Inverpolly area, however it was to be retained for Knockan Crag.

[3] The NNR is part of the wider Knockan Cliffs Site of Special Scientific Interest,[17] and is classified as a Category III protected area by the International Union for Conservation of Nature.