A vital witness is being asked to come forward as he might hold key information about an alleged sexual assault on a young woman in Gravesend.

A 21-year-old woman was approached in an alleyway between Cedar Road and Ifield School in the Kings Farm area of the town.

The woman did not know the man and it is believed he stopped the attack when another man entered the alleyway and walked past them.

DC Mark Donovan said: "I believe this person might be able to assist in our inquiries and would urge them to contact me on 01474 366043 as soon as possible."

The attack took place at about 5.30pm on Wednesday, April 2 but police only released details today.