Serial killer Stephen Port was "obsessed" with watching drug rape pornography and messaging men online, an inquest has heard.
The 46-year-old was given a whole life sentence in 2016 for murdering four men and sexually assaulting several others.
Anthony Walgate, 23; Gabriel Kovari, 22; Daniel Whitworth, 21, and Jack Taylor, 25, were killed between June 2014 and September 2015 after Port gave them overdoses of the date rape drug GHB.
He dumped their bodies near his flat in Barking, east London, just yards from where the inquest into their deaths is taking place.
It will examine whether there were police shortcomings in the investigations and whether lives could have been saved.
Giving evidence at Barking Town Hall, Detective Inspector Mark Richards detailed his work on Operation Lilford, which was launched after the four deaths were linked in 2015.
He said Port's laptop, originally seized during the investigation of Mr Walgate's death, showed hundreds of thousands of lines of messaging about sex, pornography and drugs.
"It was absolutely incessant," he told the jury. "It was all day, every day, line after line.
"There were hundreds of thousands of lines of messaging because he was absolutely obsessed with messaging."
Port would watch "a considerable and extensive amount" of drug rape pornography, viewing it for hours at a time on his laptop.
The officer said: "He had a real obsession with drug rape pornography."
Port would arrange to meet men at Barking train station and take them back to his flat.
The inquest was told how he would watch pornography "almost up to the point of meeting them", before continuing to view the material once the men were in his home around half-an-hour later.
Port began taking GHB in late 2013. At his Old Bailey trial, the former chef was found guilty of drugging and raping seven living victims as well as the murders.
The inquests were told how police have identified six additional living victims who did not wish to take part in the prosecution.
Detectives reviewed nearly 60 other deaths in the Barking area to ensure Port had not claimed any more lives.
But police still do not know how he transported his victims' bodies from his flat to where they were dumped.
Mr Richards said their theory was that 6ft 5in Port wrapped them in bed sheets and carried them "as if you're carrying a child to bed".