Leeks

Most of the food history books I've been reading over the last two years have been really interesting, but once in a while they throw out something without enough detail.  For instance, in Martin Elkort's The Secret Life of Food, I came across the information that in 640 C.E. the Welsh army pinned leeks to their clothing before battling a British King and they won, so the leeks got the credit for the victory and that leeks have been a symbol of good luck for the Welsh ever since.

Okay.  I know that at the time--and for hundreds of years afterward--victory in battle was generally attributed to anything except army size, luck or prowess.  I get that.  But why did the entire army decide to pin leeks to their clothing in the first place?  Did they have really big pins or just really small leeks?  Was the entire onion family associated with battle, or just leeks? Were they pinned there for snack purposes?  Was the opposing army also sporting vegetable matter?      

And how "urban" did the world have to be before "urban legends" surfaced?  Call me cynical, but I'm thinking this one has to be a legend or typo somewhere along the line.......