Howard Stern tried to apologise to Robin Williams for a bad interview. He was too late.

If we looked up ‘shock jock’ in the dictionary, we wouldn’t be surprised to see a photo of Howard Stern.

Stern’s long-running, controversial radio show regularly made headlines – he had a long-standing feud with Rosie O’Donnell and Donald Trump was one of his most regular guests.

But upon reflection, Stern, 65, has regret over how he handled interviews with many of his guests.

“In my mind, I knew all the answers. The audience won’t sit still for anything that’s more than 30 seconds long, he told Rolling Stone. “All they want is to be shocked and outraged. That’s where I was at in my life.”

Robin Williams, we miss you. Post continues below video.

He has since called a few past guests to apologise for his behaviour, but there was one man he never got a chance to make amends with.

“I also have a regret about Robin Williams that haunts me. I was so angry at the world. . I’d be, ‘F–k you.'”

He explained he was more concerned about keeping the attention on himself rather than focusing on his guest – such as Robin Williams.

During the interview, Stern took aim at Williams’ cheating scandal with his son’s nanny Marsha Garces, who he would later marry.

"I was a baby. I want every listener. I want everyone focused on me. You’re not going to be funnier than me. You’re not going to come into my studio and steal the moment from me. This is who I was.

"Rather than say to Robin Williams, ‘My God, you’re here,’ and celebrate an amazing talent and the beauty of that guy’s career, he walks in and I start in, ‘Hey, you’re f**king your nanny."

Stern said psychotherapy helped him learn there were other ways to talk about things.

He said he loved Williams work and regretted not telling him. He decided he needed to reach out - but it was too late.

"I could’ve expressed to him the beauty of Robin Williams. Who knows what he would have revealed? Who knows what impressions he would have broken into? It brings me to tears to imagine what that moment could have been like," Stern said.

"I had this idea that I gotta call him and apologise. I started to put it in process and see if he would take my call, but he killed himself. I get chills when I tell you."

Williams died in 2014 aged 63 after an intense battle with a pernicious neurodegenerative disease that was slowly eroding his mind.

Those close to the legendary actor thought he had depression and in May 2014, Williams had been diagnosed with Parkinson's disease.

On August 10, 2014, Williams said goodnight to his wife Susan and retired to his room.

“As we always did, we said to each other, ‘Good night, my love’, ” Susan explained in biography Robin.

“He seemed like he was doing better, like he was on the path of something.”

The next morning, Susan discovered Williams had taken his own life.

Three months later the autopsy showed the veteran comedian had been suffering from “diffuse Lewy body dementia”.

He wasn’t depressed and he didn’t have Parkinson’s – an incurable brain disease had slowly robbed Williams’ of his life force.

Lewy body dementia, also known as dementia with Lewy bodies, is a progressive brain disorder characterised by microscopic protein deposits, called Lewy bodies, that develop on the brain.

It’s the second most common form of dementia, but it’s often misdiagnosed as Parkinson’s disease or Alzheimer’s. The symptoms include sleep disorders, hallucinations, impaired movement, difficulty judging distance, confusion, and memory loss.