Thanks for posting this little beauty Nicola.
Its a nice plant to have in any collection.
I have what I understand is Viola labradorica Nicola.
It was given to me long ago by a very good gardener.
This website:
http://www.perennials.com/plants/viola-labradorica.htmlsays that it is now correctly known as Viola riviniana Purpurea Group.
How can we mere mortals keep up with these name changes
Anyway, I agree with their description- its a charming violet.
It Self-seeds gently around the garden - Yes
but not in a weedy sort of way - yes.
Sometimes troubled by slugs. Don't agree with that (my experience only of course)
My garden is infested with the things and I havent noticed any damage.