Bulgarian Giant Leeks

I couldn't resist something I saw in the Dobies 2009 seed catalogue. This picture caught my eye, and I thought I would have to get some Bulgarian Giant Leeks. From this photo it looks as if they might reach about 2 or 3 feet long! Has anyone tried them? Seed packet arrived in the post this morning.
I might try growing batches in succession throughout the Summer and see how hardy they are. I just love leeks because they are the only thing still standing on the allotment right the way through the Winter.