A 50-year-old man was arrested in connection with the murder of Earlsfield sex offender Andrew Cunningham - but was later released.
The arrest took place at 9am on Thursday, July 9, but he was then bailed while police continued their inquiries.
Despite a £20,000 reward issued in June for information leading to the killer, police say they still have nothing concrete to go on.
Detective Chief Inspector Nick Scola said: “We are still appealing for witnesses. We are no nearer to solving the case.”
Mr Cunningham, who was convicted of unlawful sex with a 15-year-old girl in 2001, was last seen at 6.10pm on Tuesday, December 9, outside his caravan in Riverside Road.
The 52-year-old was found dead the next day with his genitals mutilated and with stab wounds to the head, neck and chest.
Police later said raiders had ransacked the caravan, opening Christmas presents and stealing a wallet containing up to £6,000.
A Scottish £100 note was also missing, but no far no-one has come forward to say they have seen it.
In June an audio clip was played on Crimewatch but it lead to yet another dead end.
Although locals assumed the murder was connected with Mr Cunningham’s sex conviction, police have said they believe it was a burglary that turned violent.
Officers are still looking at CCTV footage, forensic tests from the caravan and the background and lifestyle of the victim.
Two people were arrested at the beginning of the investigation, but later released.
The third man was bailed to return to a south London police station in early September.
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