Robin Williams improvised enough for "almost two million feet" of 'Mrs Doubtfire' footage.

Director Chris Columbus has recalled how late star Williams - who tragically took his own life aged 63 in 2014 - suggested working on "three or four scripted takes" before having some fun.

Speaking to Business Insider, he said: "It got to the point that I had to shoot the entire movie with four cameras to keep up with him.

“None of us knew what he was going to say when he got going and so I wanted a camera on the other actors to get their reactions…

[The studio was] loving what they were seeing. Did they watch everything? I don’t think so. We shot almost 2 million feet of film on that picture.”

Three decades later, Columbus has kept over 900 boxes of footage including heaps of outtakes and unseen behind the scenes clips, and he'd love to turn it all into a documentary.

He added: "There are roughly 972 boxes of footage from ‘Doubtfire’ — footage we used in the movie, outtakes, behind-the-scenes footage — in a warehouse somewhere and we would like to hire an editor to go in and look at all of that footage.

“We want to show Robin’s process. There is something special and magical about how he went about his work and I think it would be fun to delve into it.

"I mean, there’s 2 million feet of film in that warehouse so there could be something we can do with all of that.”

Meanwhile, the filmmaker still feels sorry for the "poor script supervisor" who had to keep up with Williams' constantly changing takes during a time when she had to handwrite everything.

He recalled: "So Robin would go to a place where he couldn’t remember much of what he said. We would go to the script supervisor and ask her and sometimes she didn’t even get it all.

"Often, he would literally give us a completely different take than what we did doing the written takes.”