Johnston's Blue

A type of geranium, this really is a superb border plant. Unfortunately it doesn't remain in flower for very long. But when it does, it demands to be noticed, especially in a large clump, such as here

 

Pretty sure that variety was mentioned on Gardeners World a few episodes back as "if you're going to get a Geranium make sure you get one of the High performers, as the ordinary ones are disappointing". I've got a note of "Johnston's Blue" in my file-of-such-things and pretty sure that was a result of Gardeners World recommendation. All i have to do now is get a plant!