Ant Invasion

It is great to see the flowers starting to appear in my strawberry pots, but not so great to see that one of the pots has been invaded by ants. I have had several attempts to get them under control - all of which have failed miserably. In fact the population seems to be increasing.

Any suggestions welcomed.

I have posted another and not very good photo in the extras because I am curious. One of these ants has wings and is much larger than the others. Is it a queen? And if so, what is she doing wandering around outside on a warm, sunny afternoon?  I thought her role was in the nursery.