Blue flower unkown.....

I was at my friend Bob's tonight, and I got there before he returned with Dimairt. - Bob takes Dimairt for a walk while I'm at school on Fridays.

I had a wee wander around his garden, and came across this flower. Bob's late wife, Diana, gave me a cutting of this flower some time ago, but mine died off much earlier on in the season. I was really surprised to see it still in bloom in Bob's garden.

I have always thought how beautiful this flower is - it resembles a thistle in some ways; but I don't know what it is called - does anyone out there know?