getting married etc

[Nan]

Hello
My partner and I want to get married before my UK work permit runs out at the end of November and we intend to stay in the UK. I know we need to apply for the certificate of approval before we can register our intention to marry, however my fiancee is dual nationality Australian/ British and has both passports. The form mentions that we may need his parent's wedding certificate if his nationality is based on a relative's nationality but this is a little vague. My partner's father is British but my partner was born in Australia and has been living in the UK for 7 years with a UK passport. Do we need to provide the wedding certificate if he has the UK passport?

any info much appreciated.

N