Identify this blue plant?

Hi all,
I do know the name of this plant, but for the life of me I can’t remember, it looks like it’s coming to the end of flowering, it has been covered in loads of very deep dark blue flowers, any idea?
Would like some advice on when to prune it back? Straight after the last flowers have gone? Is this in general for most flowers once they have finished flowering?
Cheers all.

 

Maybe Lithodora Diffusa
I was considering using it to edge my pond, but my soil won't suit it

 

Thanks Pete, that's the one......

Would it be a good time to prune it after flowering do you think?

 

I don't know, but pruning after flowering is the norm.
I thought it looked really nice, but when I realised it wouldn't suit my soil I bought creeping thyme instead and didn't research it any more.

 

The RHS says it’s pruning group 8, which means it might not even need it. But if you want to, mid-late spring is the time. I think my previous neighbour had this one, and I don’t think she pruned it. Maybe it depends on how it grows in your conditions.

 

I tidy mine up in late winter/early spring to remove any tired foliage and stems but then let it keep going until it outgrows its space or gets untidy. It can be reduced in size by about a third without causing any harm.