Documents compiled by North Yorkshire Police indicate he was taken to a massage parlour in Leeds just hours after making his first statement providing information about the murder of 85-year-old Joe Smales in Wakefield.
Chapman was given £475 but returned to prison the next day with just £6.73 in his pocket.
When Chapman met North Yorkshire detectives in May 2006, he said he spent £150 on sex and £300 on clothes when police escorted him back to prison.
Letters uncovered by North Yorkshire officers included one written to Chapman by Dc Derek Dunham, a week after the trip.
It said: “Thanks for the letter and really glad you enjoyed ‘the night’.
“Truth to tell I quite enjoyed it myself. Little bit of this, little bit of that. Variety, they say, is the spice of life. What a spicy night.
“Let’s hope there is a second leg in March, I’m demob happy now and disinclined to dip out on any good times that may be up for grabs.”
Another one written by Chapman to Pc Shirley Faulkner, a woman he had a relationship with, included an apology for visiting a “knocking shop”.
It said: “I was furious when he (Dunham) told you about my visit to one... What was I supposed to do? I was drunk and stoned on weed, they paraded a dozen beautiful women in front of me and said take your pick.
“It’s a week before Christmas. I thought I’d never see you again. I was due back in prison in less than 12 hours.”
Dc Dunham, who retired a few months later and moved to Spain, talked to North Yorkshire Police officers in 2006. He recalled being out on December 10, 1996 with Chapman who needed “TLC” after his “historic statement”.
Although he denied visiting the brothel, investigators concluded the trip did take place.
The Criminal Case Review Commission concluded: “The fresh evidence surrounding the circumstances of this payment demonstrates the inadequacy of the custody record and the paucity of information on the schedule of disclosed payments.
“Had the defence been aware that Mr Chapman had spent £468 in less than a day in police custody, they may have made further inquiries about the circumstances in which he had been able to do so.”