Hi this is Linaria, common name purple loostrife.
It is easy and hardy. It seeds freely, doesnt need staking and generaly pest free.

If this isnt the same one you were asking about yestreday then that id was wrong.

I imagine that the Lobelia died and the Linaria purpurea seeded into the space. It will seed around a lot unless you remember to deadhead it. Cut down the tall shoots now but leave any leafy short ones. In Spring it will throw up more shoots and flower for you. There is a lovely pink form called 'Canon Went' that you can buy as seed.

it looks like purple toadflax to me

Seaburngirl-No, its a different plant.

can you do some good close ups of the leaves and stem and any seed heads for the other one then please.