I went to this location and found:

UFO over Cathedral Causes power cuts in UK historic town.

I found the last part of the article interesting from the viewpoint of comparing the idea of possible alien behaviour to the behaviour of humans.

All this begs the question, are visitors from space interested in our history and going on tours of places of historical significance? After all this is not the first sighting in this area in recent months. The more pessimistic amongst ufologists have a far more worrying theory: The aliens might be documenting our history prior to putting into action a plan that will either end it altogether or change in forever.

Let's use our imagination for a while.

Suppose that we were able to travel freely in space, sort of Star Trek style.
Now suppose that, for years, we had been observing the development of technology on a planet that was nearby our own planet.
Now suppose also that these beings/people are very warlike, killing each other at the slightest provocation or even suspicion of attack from the other party.

What would we do if they had thousands of nuclear weapons piled up and were on the verge of having the ability to launch those nuclear weapons at us.

Would we try to communicate with them, would we use a pre-emptive strike and blow them out of the sky, would we allow them to develop their abilities and hope they will see the error of their ways, would we move to a different galaxy and wait until they can catch up.

What do you think?
What would you do if you were the decision maker that had to make the final decision?