Then, in 2010, Turner played several characters including the mother of late playwright Timothy Conigrave in the theatrical adaptation of Conigrave's autobiography, Holding the Man, in London's West End.

Turner drew on experience: she was a high-school friend of Conigrave and his lover, John Calleo, who both died of AIDS-related complications.

Now, Turner is standing up for same-sex marriage. She will be reunited with her co-stars in the theatre production, Guy Edmonds and Matt Zeremes, who played Conigrave and Calleo, in a feature-film musical that will begin shooting in the new year. The film is called Super Awesome!

Edmonds and Zeremes have written and will star as two straight composers who want to write a Broadway/West End-style musical about same-sex marriage – but who are clueless on the topic.

The comedy musical has a subversive aim: using what Kath of Fountain Lakes would call 'umour to make the Parliament allow same-sex marriage.

"I haven't seen the final script but they're finessing the final draft," says Turner, who's to play Deb, the owner of a comic-book store.

"They gave me an outline of the story and it sounded really funny, just up my alley, camp and musical, and I trust them to make something good and really funny."

Turner is "totally pro-" on same-sex marriage: "I don't see why homosexuals and lesbians should be treated any different to others and not have the exact same rights.

"It's all about love and sharing and commitment to each other so I can't really see what the big drama is. There are plenty of problems in the world we should be focusing on rather than something negative like anti-gay marriage."

Edmonds and Zeremes, both of whom identify as heterosexual, are also committed to reforming legislation to allow same-sex marriage. The pair – neither of whom will sing in the movie – will soon announce the full cast.

Edmonds and Zeremes say Super Awesome! will have a "light touch".