Thames Valley Police is appealing for specific witnesses in connection with a sexual assault in Bletchley, Milton Keynes.
The victim, a woman in her forties, was walking along Sherwood Drive at about 1pm on Wednesday (24/7).
As she walked past Bletchley Park, a man grabbed her, before sexually assaulting her.
The victim managed to break free from the offender, who then fled the scene.
The offender is a white man, tanned, in his twenties, stocky, with hairy arms, stubble and black hair, which was gelled back and in a side parting.
He was wearing a black polo with three buttons done up and yellow writing on the chest, black smart cargo type shorts with a pocket, and a ring.
He spoke with a local accent.
Investigating officer, PC Martina Pecorini said: “I am appealing to specific witnesses in connection with this sexual assault to contact police as soon as possible.
“The first witnesses are the driver and any occupants of a vehicle that was driven past the scene at the time of the offence.
“The other witness is a Good Samaritan who checked on the woman’s welfare following the offence. This witness is a black man who was near the flats in Turing Gate.
“If you are one of these witnesses or have any other information about the offence then please contact police. You can visit our website here or call 101, quoting reference number 43190226566.”
