United Kingdom, July 31 -- Francis Ford Coppola has celebrated the 30th anniversary of Jack with a heartfelt tribute to the Robin Williams film.

Describing it as "imaginative and unusual" and defending a project that divided critics on its original release, the Oscar-winning filmmaker, 87, marked the milestone of the movie on Instagram through his production company, American Zoetrope, by sharing a rehearsal clip from the 1996 film.

The footage features Robin Williams, who died by suicide in 2014 aged 63, improvising with co-star Adam Zolotin, who played the young Louis.

The anniversary comes as Francis continues to attract attention following the release of his self-financed epic Megalopolis, while his wider body of work - including T...