https://phys.org/news/2018-10-lamprey-teeth-london-archaeological.html

The story goes that Henry I had such a hankering for this scary snack that his doctor deemed the cause of his untimely death "a surfeit of lampreys" – though this may be a fanciful embellishment on the part of Henry of Huntingdon, his chronicler. Even recently, they have been popular with the royals: a lamprey pie was made for the coronation of Queen Elizabeth II in 1953.

As lampreys have no bones or jaws, they leave little trace in the archaeological record. They are only known from two other sites in the UK: Coppergate in York and Dundrennan Abbey in Scotland. Even their 'teeth' are unlikely to be preserved, since they are made of keratin (the same as hair and nails), which is much softer than enamel or dentine, making this discovery all the more remarkable.