Hi Malcolm,
The short answer is that group sizes have been limited to six by new guidelines, the long answer with links to the documents from which we based our decision is at https://www.ldwa.org.uk/library/coronavirus2020.php.
The Ramblers are indeed allowing walks of up to thirty people, but they still have to walk within smaller groups of six and those sub-groups cannot interact (see the FAQs on Ramblers group walking). For shorter walks, this may be a little more manageable, although still very challenging. For long-distance walks of eighteen miles, trying to keep these sub-groups apart and with no interaction would be enormously challenging and it would be a push to describe these as social walks.
However, walks of up to six people are still encouraged and many groups are offering these. We will continue to review the Government advice, but we want to be within the law and also the spirit of the guidelines, even if there is perhaps not the clarity that we'd ideally like at the moment. I would entirely agree that the situation with football match crowds is unfortunate when we're not allowed to walk in group sizes above six, but hopefully this is just a temporary measure.
Julian.