Robert Downey Jr's nuptials with producer Susan Levin will be a grand affair, styled after classic movie The Great Gatsby.

The lovebirds will wed tomorrow (27AUG05) in the sprawling Hamptons, New York, grounds of billionaire Ron Perlman and his wife Ellen Barkin's estate, and the actor is "going all out" to ensure the day is as grand as the venue.

A source says, "The is going to be an extremely lavish wedding, so Robert can show how serious he is about her being in his life forever."