Who is the woman in taupe with the monstrous tentacled hat seated directly behind Queen Elizabeth (who is wearing yellow) during the wedding ceremony?

See ALL the royal wedding footage. This hat must be either from hell or from Fluther. Giant taupe tentacles curl up above the Hat and more hang down alongside. After one long take, in subsequent footage she was not in the picture. Close up on Queen who looked a little like she was cringing away from The Hat. Send me screen grabs, video links.
Thanks.