Police have today released an e-fit of a man they would like to find after the offending outside the Duke of Wellington pub around 6.30pm, on January 24.
A 33-year-old woman was walking through the town centre towards a bus stop on Commercial Street when she was approached by a man.
He engaged her in conversation before subjecting her to an assault and attempting to pull her into a van, police said.
The victim shouted for help and he fled.
Investigating Officer, PC Katy Bradford said: “This was clearly a traumatic ordeal for the victim and we are treating this incident extremely seriously.
“A significant amount of work has already taken place to identify the man responsible, including CCTV enquiries.
“Working with the victim, we have now developed an e-fit to help trace this individual.
“He is described as white, around 5 foot 10 inches tall with a heavy build and had a Yorkshire accent. He was also wearing a dark blue hooded top with dark trousers.
“This took place outside the Duke of Wellington pub and it is likely that a number of people were in or around the vicinity at this time.
“Passing drivers may also recall seeing something happening and could potentially hold dash cam footage that could assist our investigations.
“If you can remember seeing this man before or during the incident, please get in touch immediately.
“You can contact the non-emergency number 101 or Crimestoppers in confidence on 0800 555 111.”