Following one of the largest and most complex manhunts in Australian history, we saw the arrest and conviction of Ivan Milat.

Milat was found guilty of the backpacker murders, where he murdered seven young people in the Belanglo State Forest between 1989 and 1993.

He now languishes in Goulburn supermax prison, obsessed with his profile in the media and often penning letters protesting his innocence.

His latest letter stretches more than 10 pages.

It details why he believes he’s an innocent victim of a corrupt judicial system, “among many other musings that border on the insane,” says Chris Smith.

Clive Small, who led the investigation behind Milat’s arrest, tells Chris it’s “a load of rubbish”.

“He ignores completely the evidence that’s against him.”

Mr Small says “it’s very frustrating” that no one is challenging Milat’s letters.

“The amount of evidence, if it’s listed, it leaves no doubt that he’s the murderer of the seven [backpackers].”

Click PLAY below to hear the full interview with Clive and Amanda

But best-selling crime author Amanda Howard has revealed to Chris Smith that she is challenging Milat’s protests, and his writing a book with him.

She says she’s been interviewing Milat “for more than 20-odd years now”.

“I go to him with each piece of evidence and say to him, ‘Explain this to me then’.”

Ms Howard describes her relationship with Milat as “interviewee and interviewer”.

“Ivan and I are about to write a book on me challenging him on all this evidence.”

On Milat’s most recent letter, she says he is completely “convinced of his own innocence”.

“I really believe that if he took a lie detector test he would actually pass it.”