A "significant" arrest was made by police investigating the murder of schoolteacher Sabina Nessa in a London park.
Metropolitan Police said a 38-year-old man was arrested in East Sussex on Sunday morning.
"Sabina's family have been informed of this significant development and they continue to be supported by specialist officers," Detective Chief Inspector Neil John said.
On September 17, Nessa was attacked while walking in Cator Park, Kidbrooke, south-east London, to meet a friend at a pub near her home.
Her body was discovered by a member of the public the next day under a pile of leaves.
Hundreds of people gathered in Cator Park to remember Nessa and call for greater attention to be given to the safety of women in public spaces.
Her death, like that of Sarah Everard, who was abducted and murdered by a serving police officer, has galvanised public opinion.
Jebina Yasmin Islam, Nessa's sister, broke down as she addressed the crowd in Cator Park.
"Words cannot describe how we are feeling, this feels like we are stuck in a bad dream and can't get out of it. Our world is shattered, we are simply lost for words. No family should go through what we are going through," she said.
On Thursday evening, investigators released CCTV images of a man they said they wanted to interview, and one of a silver car. It is understood they are no longer following this lead.
Two men were separately arrested in connection with Nessa's death. They have been released.