This is a plant which is growing on the gravel shore of Southampton Water and has defied my efforts of identification. It looks a like a type Eryngium to me but perhaps someone else can tell me different?
Think this might be Sea Kale (Crambe maritima), Baa. Certainly worth investigating. Described by Keble Martin:
"Stem 1-3' leaves broad and fleshy (the ones i've seen i'd describe more as leathery) flowers white (June-Aug have to have another trip) pods spherical or oval."
I originally thought it was Crambe, in fact I named the jpeg SeaKale but the leaves are flat on the above plant where as Crambe maritima tends to be folded along the midrib and all wavy, the leaves of Crambe are also much larger.