The Danish Girl drew long applause from global journalists after its Venice world premiere screening and raised plenty of timely transgender issues at its subsequent packed press conference.
Eddie Redmayne, whose performance is already generating awards buzz after his Oscar for playing Stephen Hawking, said the whole process for him "was the most mammoth education."
"I met many people from the trans community, both men and women. I tried to meet people of different generations because the story is set at a time [between 1926 and 1931] when there was no precedent.
"Across the board the generosity of people was amazing. There was one particular couple in Los Angeles, a woman called Cadence and her partner Trista; they had been together when she was living as a man, and they are still together," Redmayne recounted. "They allowed me to ask anything.
"There were two things Kadence said: one was that she would do anything and everything to live a life authentic, and the other thing was in relation to her partner. While she was transitioning, the question for her was: 'How deep was her partner's pool of empathy?' Those two things sat with me all the way through the whole filmmaking process."
About Redmayne's preparation, director Tom Hooper said, "From the very beginning we talked in terms of the idea that Eddie was playing a woman that was going to be revealed. So rather than it being a process of how Eddie might learn to imitate a woman it was about how he might create the impression that he was uncovering a latent femininity, a woman inside. This guided us through the process."
Answering an odd question about the whether a sex-change operation can be considered a crime from a purely medical standpoint, Hooper said, "The world has shifted profoundly on Lili's story. I hope now that a trans woman or trans man going through transition would not feel the same pressure to go the surgical route if he or she did not feel comfortable with that.
"I would champion any shift where the industry could move forward and embrace trans actors in trans and cisgender roles and also celebrate and encourage trans filmmakers."
"I think to some extent that the villain in the piece, if there is one, is dualism. The idea that there is a duality. That if you are not a man you have to be operated on fully to become a woman. That if you are not a woman, you need to be surgically corrected to be a man. I do think we are evolving beyond the binary and thinking about gender as a spectrum. There can be very complicated places on that spectrum."
Asked why he did not pick a transgender actor for the lead role, Hooper replied, "Access to trans actors, women and men, to roles, both trans roles and cisgender roles, is utterly key, and I feel that within the industry at the moment there is a problem. There is a huge pool of talented trans actors and the access to parts is limited. I would champion any shift where the industry could move forward and embrace trans actors in trans and cisgender roles and also celebrate and encourage trans filmmakers.
"In terms of the casting of Eddie, I'm going to say something that would be easier to say if Eddie weren't sitting next to me, but I think there is something in Eddie that's drawn to the feminine," he added.
But ultimately The Danish Girl is a love story, as Alicia Vikander, who plays Gerda Wegener, the woman artist who is married to Lili before her transition and supports her throughout, pointed out.
"Like everyone else I was attracted to the extraordinary love story that is extremely passionate and extremely unique," she said. "I fell in love with the fact that it's just a love story between two people. Above all it's a story about how to love yourself. Gerda was extremely ahead of her time."
Watch 'The Danish Girl'
Thursday 31 December, 2:10am on SBS VICELAND (NOTE: No catch-up at SBS On Demand)
UK, USA, 2015
Director: Tom Hooper
Starring: Eddie Redmayne, Alicia Vikander, Matthias Schoenaerts, Amber Heard, Ben Whishaw