Steven Spielberg has revealed the brilliant way Robin Williams helped him through the strenuous shoot of his war drama Schindler's List.

Speaking at a retrospective event taking place at Tribeca Film Festival, Spielberg - who was accompanied by stars Ben Kingsley, Embeth Davidtz, Liam Neeson and Caroline Goodall - recounted how the late actor would call him weekly for the sole purpose of performing comedy over the phone to cheer him up.

“He would call and do 15 minutes of stand-up on the phone,” Deadline reports the filmmaker as remembering with a smile. “He would never say goodbye; he would always just hang up on the biggest laugh he got from me. Mic drop.”

The event marked the first time Spielberg had watched the drama - which won seven Oscars - with a full crowd since it was released in 1993, an experience he said filled him with a greater sense of “meaningful accomplishment” than he's felt on any film he's made since.

Spielberg also used the opportunity to debunk and confirm some long-standing rumours surrounding the film. He stated that Mel Gibson was never considered for Neeson's role of Oskar Schindler, the businessman who saved the lives of thousands of refugees from the Holocaust, but revealed that Martin Scorsese was in the running to direct.

The film's gathered cast members recalled with shudders how anti-Semitism seeped onto the film's set recounting how Swastikas would regularly appear on walls around them. “It was just for us,” Kingsley added, as Spielberg remembered a woman communicating to Ralph Fiennes, who was wearing his character's S.S. uniform, that she wished the S.S. were still there to protect him.

Deadline also reports a moving anecdote from Neeson who recalled an encounter with one of the film's producers, Branko Lustig, outside the gates of Auschwitz where they were shooting a scene one freezing morning.

Neeson added: “He pointed over to the huts at Auschwitz and he said, 'You see that hut? I was in that hut.’ It hit me, big f***ing time. Big time. I kept screwing up all the lines."