I think the point that your parent commenter was making is that Oxford is in the UK and the UK is no longer a member of the EU or Euratom, although it has various agreements with both.
It's probably related to brexit in that this outlook is very likely at least part of why Brexit happened (or rather why the UK was never a particularly good fit for the EU)
Or will this fusion go out of control and demolish the UK in a nuclear fireball?