Very pretty herbaceous plant which grows readily in our climate. However, to see it flowering at the end of January is most unusual, and is only due to the damp conditions we have had this year.
I'm not complaining - it's gorgeous at the moment.
EDIT - I got it wrong - it's Self Heal Prunella vulgaris - a medicinal herb of European origin - also a member of the Mint family. The spike of flowers just isn't expanded enough for an Ajuga, which have whorls of flowers interspersed with leaflets, which have a crenate margin. Thanks Mollyblobs!