A young woman was sexually assaulted in a Northampton street by a man wearing a distinctive rainbow T-shirt.
The woman was in Bostock Avenue, Abington, on Saturday, July 11, when she was approached by the man sometime between 11pm and 11.30pm.
He sexually assaulted her before two members of the public intervened and he ran away.
He is described as white, in his 30s, between 5ft 8in and 5ft 11in, with short blonde hair.
He was of large build and wore grey trousers and a white T-shirt with a rainbow logo on the front.
Officers investigating the case have released both a computer generated image and a CCTV picture of the man they believe committed the offence.
They would like to speak to anyone who recognises the description of the man and are particularly keen to speak to the two young men who went to help the woman.
It is believed they had previously been parked in a silver car in Bostock Avenue.
Witnesses, or anyone who knows anything about this incident, can call Northamptonshire Police on 101, or Crimestoppers on 0800 555 111.