It was organised via Facebook and the (optional) annual membership fee was £2 so I haven’t lost out financially but it’s still a shock!
The organisers posted that they’ve discussed it and decided that they had to close. They wrote that they’re not going to discuss this and that the group will be shut down after 24 hours. It’s currently paused (which, it seems, means that members can still see the group but nothing new can be added).
There’s obviously a demand for a local club so I’ve set up an alternative group. We currently don’t have any qualified coaches so it’s really just a group for organising runs with friends. It looks like I could end up operating a running club!