Sacks, whose book Awakenings inspired the Oscar-nominated movie starring Williams and Robert De Niro, lost his battle with cancer on Saturday (29Aug15) just over a year after the actor took his own life last August (14).

Williams' daughter Zelda has now shared her sorrow for her longtime family friend, who was also a neurologist and wrote a series of books about unusual medical conditions, writing in a post on, "Last night, we lost one of the brain's greatest champions, as well as one of my family's favourite humans. Thank you Oliver, for treating humans like humans, not patients, and for how much you did and will continue to do for mental awareness. Here's hoping you and Dad are enjoying the view together, and debating the world again the way only you two could. RIP. Mr. Sacks..."

She also shared two photographs showing her father and Sacks chatting together, adding the caption, "I love to discover potential in people who aren't thought to have any... - Oliver Sacks. Missing you both, always."

Zelda recently returned to social media following a month-long "cleanse" as the one-year anniversary of her father's death loomed.