Detectives investigating an alleged sexual assault are appealing for help in tracing a dog walker.
The alleged incident happened in the late afternoon or evening of Wednesday December 2, in West Park, Long Eaton.
A woman told police she had been walking through the park with a man who then sexually assaulted her.
A short time later, the pair were walking out of the park and stopped to speak to a man who was walking three dogs on one lead.
Detectives investigating the allegations want to trace the dog walker to see if he has any information that could help.
The dog walker was wearing a woolly hat and a bomber jacket, and was walking what were thought to be two Staffordshire bull terriers and a German Shepherd.
Anyone who was walking through the park, off Wilsthorpe Road, around that time on December 2 should call Derbyshire police on 101, quoting crime reference 52171/15, or Crimestoppers anonymously on 0800 555 111.
A 50-year-old man was arrested in connection with the investigation and has been bailed pending further inquiries.