A woman was grabbed by the neck and repeatedly raped near a busy central London road, police said.
The woman had been walking in the area of Great Dover Street in Borough at about 2.15am when she was allegedly attacked.
Scotland Yard said she was grabbed from behind, threatened, and taken to a wooded track leading from Brockham Street to Dickens Fields by a stranger, who raped her a number of times.
She managed to escape and run to Trinity Church Square but was caught up by the suspect, at which point a car stopped, police added.
"The suspect exchanged some words with this driver, who then left," a spokesman said.
"Almost immediately afterwards, either the same car or a different car stopped and the victim managed to escape to the safety of the vehicle whereupon the suspect walked off."
The Metropolitan Police said they would like to speak the man who drove the alleged victim to Walworth police station in the early hours of July 20.
He is thought to be a black male in his early 20s who was possibly driving a seven-seater vehicle.
Detective Sergeant Jonny Norman, who is leading the investigation, said both drivers are being treated as possible witnesses.
"We are very keen to trace the driver of the vehicle who drove the victim to Walworth police station," he said.
"Did you drive a distressed women to Walworth Police Station, in the small hours of Saturday July 20? We would like to speak to you to support our ongoing investigation.
"We would also like to speak to the first driver who originally stopped, although unfortunately we do not have a description of this person.
"We are treating both of these individuals as possible witnesses and we would like to highlight that you are not in trouble."
Officers are also linking this incident to a separate alleged sexual assault on another woman, reported to have happened a short time afterwards in Borough High Street.
Anyone with information about either incident is urged to contact police via 101, or by tweeting @MetCC quoting CAD reference CAD 6111/02Aug19.
A 28-year-old man has been charged in connection with offences against both women, and will appear in court at a date in late August.
