Might be a Phlox

Thanks Drc726 but I think leaves are a bit rounded rather than pointy for a phlox.

Could it be night scented stock? My next door neighbour has them in her garden and swears she didn't sow them.

Yes that might be so as the leaves do look as if they might grow wider Aiman. I think it might turn out to be a low ground cover as those lower leaves look as if they might grow longer?

Is it some kind of Periwinkle?

That looks exactly like the stocks that I have grown from seed in my flower bed. I'll check the packet for the proper name.

I think it is a periwinkle too.

Look like Stock flower to me. Mine came into flower last week - just throw the seeds into an empty bed and forgot about them. They are self sowing annuals.