What is this plant please?

Does anyone know what this plant is, please. It grows profusely on a very dry chalky bank in the garden. I've wondered about it for 6 years and today I went through three flower books looking for it - and others.

It is about 25cm tall, grows in a big bunch, has alternating dark green ribbed leaves and these bunches of tiny red flowers (which I only noticed today) down in the crux of the leaf stems and stalk.

I'm up to 276 plants on my list from yesterday. It would be nice to get 300 but if they are not there they are not there.