Actually it is a "choken" . It is used in table games but is metal in nature.
To the best of my memory, it was issued in the year 1999 as a millennium piece.
There also exists another version of this from the same Casino. It is the same basic design however it is pink in color and depicts a ladybug in the center.

A similar "choken" was also issued by the Connoisseur casino. That one is a 5 pound piece, Red in color and has a design of a club [ As in the card suit]

I can not tell you which particular casino issued the Grosvenor chokens. Grosvenor operates quite a few establishments in England