What is the plant which is growing in my garden, and how can i get rid of it?

[smashvee]

There is a plant which is growing in several areas of my garden. I didn't plant it as it was here when I moved in, and I have no idea what it is. It grows to about 1 meter tall, but flowers in summer and the flowers are quite tall. It has large dark green foliage (approx. 30cm) with some spikes or prickles around the edge. at the end of summer, it dries up and the foliage disappears. What is left of the flowers goes brown and looks somewhat like a dried thistle. At the end of the summer, I removed all traces i could, but come spring, the foliage has regrown. It has quite a deep root system, and the roots snap easily when i try to dig or pull them out. What could it be? and how can i get rid of it?