Police are questioning a 40-year-old man over the 1992 murder of young mother Rachel Nickell.
Rachel Nickell was stabbed 49 times
The 23-year-old model was sexually assaulted and stabbed 49 times on Wimbledon Common in south-west London.
It is thought the man was identified following a breakthrough in DNA testing. It is believed he is being held in Broadmoor.
Ms Nickell had been walking with her two-year-old son when she was murdered. The killer has never been caught.
The police said the interview was part of an ongoing inquiry into her murder.
In 1994, Colin Stagg was tried for the murder but the case was thrown out on the grounds that police had used a "honey trap" plot to encourage him to confess.
Mr Stagg told Sky News he would never be able to escape the consequences of being linked to the murder.
"I've always been associated with the Rachel Nickell case and I'll never shake that off really," he said.
"You will always have people who will always believe I had something to do with it in some way."