She left behind two young sons, Micheál and Daniel, as well as her famous sister Joel Richardson and mother Vanessa Redgrave.
The younger members of the family have rarely spoken publicly of their grief and loss, but a new film has been a “cathartic” process, says Liam.
When it was first announced, Micheál said: “The parallels were so apparent that it felt like my mom, in a spiritual sense, had a hand in it.”
He said, “I think the pain was a little too overwhelming.
“I think the mind is very powerful, and subconsciously, or unconsciously, it can protect you.
“That’s what it did when she passed. I just pushed it aside and didn’t want to deal with it.”
Father and son appeared on Graham Norton this week and spoke honestly about the experience of acting out a story that mirrored their own so closely.
Not only does it portray a family struggling with the loss of a wife and mother, but it also shows a son trying to follow in the footsteps of his famous father (in the film he is an artist).
Despite the subject-matter, Made In Italy is a gentle romantic comedy. Directed and written by fellow actor James D’Arcy, it also stars Lindsay Duncan.
Even so, Liam said everyone involved with the project was very aware of his family’s own story, especially when filming some of the more emotional scenes.
“There were some very delicate emotional scenes, and I could access the emotion without any problem, I didn’t need days to build up to it and I thought Micheál would be the same.
“We had such a delicate producer and such a supportive crew that we felt wonderfully comfortable.”
Micheál also talks about how “traumatic” his childhood could be with two famous parents.
“As a kid, I thought it was CGI or some Hollywood effect, it wasn’t real!”
He is, of course referring to Liam’s famous role as the Jedi master Qui-Gon Jinn, who met a grisly death in the Star Wars prequels.
The Graham Norton Show is available on BBC iPlayer.
Made In Italy is out now Amazon Prime