Growing Sicilia Violetto cauliflower

I've got some of the above cauliflower growing in the plot. This is the first time that I have tried them. They've put on a good amount of leaf and over the last couple of weeks started to form a curd. However instead of a solid ball it looks more like lots of stems with flowers on the end. Has it bolted and gone to seed or is this how it grows?

And before you ask - yes I am that dumb!

Regards, WG