In which English county is the site of the prehistoric flint mines known as Grimes Graves?

Player #48458, the mind boggles, so you know all of the other useless info from around the world and (let's face it there's plenty) just not the UK stuff. We'll go on take a guess like we all have to.

[bobbo16], you keep asking questions that Americans don't know. si'nce we don't live in the UK we can't answer them.