I can't comment on Oxbridge, but Law at most other Unis does not require any specific subjects.
Many people find an essay-based subject useful background, and elements of History and Politics may give you some useful prior knowledge, but none of this is essential. People with three science A levels manage just as well.
Politics is not seen as a soft subject. It is up there with History, English, Sociology etc.
Check for Oxbridge, but for all other Unis that combo of subjects is fine.