Lancaster Police have released a computer-generated image of a man they want to trace in connection with a serious sexual assault in Lancaster.

The incident is alleged to have taken place in an alleyway off Brock Lane near to the Horse and Farrier pub on Brock Street between 10pm on Saturday 5 September and 12.40am on Sunday 6th September 2009.

The woman met her alleged offender outside the pub after leaving friends to have a cigarette. They got talking and went back inside the pub together where they continued to drink for some time before leaving together in the direction of the alleyway where the incident is alleged to have taken place.

Officers are appealing to anyone in the pub on Saturday night that saw the couple to come forward.

He is described as being in his late twenties, between 5ft10 and 6ft tall, stocky, muscular build with dark brown cropped hair ‘number two cut’. He is clean shaven with blue eyes and an olive complexion and was smart in his appearance, wearing a pale blue top. He is also possibly known as “Ian”.

The woman was wearing black trousers and a black and white vertical striped top.

“I’m keen to trace people that were in the pub at the same time as the pair or anyone that saw them leave together,” commnetd Detective Inspector Martin Clague, from Lancashire Police’s Force Major Investigation Team. “I would also appeal directly to the man described to come forward so he can help us with our enquires.”

• Anyone with any information about the incident should contact Lancashire police on 01524 63333 or Crimestoppers on 0800 555 111.