An 82-year-old woman has been pushed to the ground and sexually assaulted in a "horrendous" attack.
The pensioner was walking in Bletchley in Milton Keynes at around 1pm on Friday 30 September when she was attacked by a man in his twenties who was dressed in black.
Police are appealing for witnesses including a dog walker and a fruit picker who may have seen the suspect or the assault.
Case investigator Samantha Arnold, from Thames Valley Police, said: "I would like to speak to anyone who may have seen or heard anything unusual on the redway running alongside Buckingham Road, behind Windmill Hill Drive.
"I would particularly like to speak to a man who was walking a dog, believed to be a white dog, possibly a husky, along the redway prior to the offence.
"I would also like to speak to a man, about 60 years old, seen picking blackcurrants near to the scene. If you know the dog walker or fruit picker, or have any other information about the offence please come forward.
"The victim is being supported by Thames Valley Police following this horrendous incident."
The suspect is a white man in his early to mid-20s and of large build. He was wearing a black beanie hat, black jacket and black trousers, and was carrying a black rucksack over both shoulders.