Sea Holly in Disguise

I have always liked the blue spikey sea hollies, Eryngium, so many years ago bought one for my garden.  I was somewhat disappointed when those lovely blue heads failed to materialise. A check on the internet reveals this is probably an agave-leaved sea holly, Eryngium agavifolium, so at least I got the genus right!  I have since bought my blue headed plant which grows alongside this one.