This article in the Guardian describes a situation which is already happening. I have personally been in two recent scientific/training network planning meetings in which UK leadership was ruled out as a possibility (by mutual agreement) as too risky in the circumstances.
I am pleased and proud that our EU collaborators are standing by us as network members though, despite the risk to them from our current political instability. We also did out best for Swiss friends during their difficulties, but as you can see from the article, the impact of isolationist decisions can’t be completely mitigated.
(Not really an article, just another tweet that got out of hand…)