Mrs. Doubtfire child star reveals important warning Robin Williams gave him that he'll 'never forget'

Warning: This article contains discussion of drug addiction and suicide which some readers may find distressing.

Matthew Lawrence has opened up about working alongside Robin Williams in Mrs. Doubtfire and the important lessons he taught him 'behind the camera'.

The 1993 hit classic - since turned into a musical in London's West End - stars none other than the legendary Robin Williams as actor Daniel, who's desperate to still see his kids as much as possible after going through a divorce with their mom.

And well, I won't spoil it, but you should really have all seen the film by now.

Matthew Lawrence played the role of Daniel's 12-year-old son Chris, the actor 12 years of age at the time himself.

Now 45, Lawrence has spoken about his experience working alongside Williams for 'six to eight months' and the lessons he learnt both professionally but also 'behind the camera' from the star.

In an interview with Entertainment Weekly after being unmasked on The Masked Singer, the actor explained working on the film was 'the biggest learning curve anyone can get when it comes to making movies and being an entertainer'.

Lawrence praised Williams as being 'the most brilliant artist' he's 'ever worked with' - and he's 'worked with some great people'.

However, he also learnt some pretty big general life lessons about what it means to be human - with Williams taking an 'investment' in every person he works with but 'really' taking one when it came to the young actor.

Williams imparted some important words of wisdom on the then-12-year-old, explaining you 'don't judge until you walk in someone else's shoes' and embodying the 'type of compassion you need to have for people' himself.

Lawrence continued: "He had the compassion, he had the humility, and he also had these things that he struggled with. He really explained his life to me and really brought me in and taught me not just about in front of the camera, but a lot about the behind the camera as well."

And Williams also opened up about 'substances' to Lawrence, saying one thing he'll 'never forget' - with Williams having previously spoken out about his addiction to alcohol and cocaine.

Matthew Lawrence worked alongside Robin Williams on Mrs. Doubtfire (20th Century Fox)

The actor recalled Williams 'really opening up' to him about 'how he felt substances really further pushed his brain to not function properly'.

Williams warned the young star to never 'put that stuff in [his] body', as Lawrence recalled him saying: "If I could go back and tell myself, this is why I'm telling you, don't put that stuff in your body."

Lawrence resolved: "I'll never forget it."

Williams passed away by suicide on August 11, 2014, Lawrence adding 'there's not a day that goes by [he] doesn't hear his voice'.

If you want friendly, confidential advice about drugs, you can call American Addiction Centers on (313) 209-9137 24/7, or contact them through their website.

If you or someone you know is struggling or in a mental health crisis, help is available through Mental Health America. Call or text 988 or chat 988lifeline.org. You can also reach the Crisis Text Line by texting MHA to 741741.