Green’s Dictionary of Slang

a mixed-race person.

1988		(con. WWII) J. Robinson Jack and Jamie Go to War 57: It was only a crowd of fackin’ wogs an’ half-chats!
2005		B. Hare Urban Grimshaw vii: Half-chat Half-caste; person of mixed-race. [Ibid.] 105: Us half-chats prefer the term mixed race.