Police have warned women not to go out alone at night after five attacks in nine days by a gang who cruise the town centre in two cars.

Jack rolling became notorious in South Africa during the 1990s, when gangs of youths in cars blocked off streets and raped every woman caught in their net.

Three women have been grabbed from the street and raped since July 31, while two more have escaped in a town where “stranger rape” is almost unknown. A climate of fear has taken hold since the latest rape, which came to light when the 30-year-old victim was found with head injuries near a housing estate in the early hours of Monday.

A blue BMW 7 Series with cream leather seats and a white or silver Fiat Punto were between them involved in three of the incidents.

On one occasion, when they appeared together, the driver of the BMW distracted the 18-year-old victim while a passenger from the Fiat bundled her into the back of the BMW. She was then driven to a remote spot on the outskirts of town and raped.

Northamptonshire Police said yesterday that this was a tactic familiar in South Africa and lent further credence to the victims’ reports that the three men involved in the attacks were black and spoke with South African accents.

Detective Chief Inspector John Jones, who is leading the investigation, said: “I may be getting in touch with colleagues in the South African police to see if there’s a trait here.”

Tracking down the cars remained the primary focus of the investigation rather than pinning down the rapists’ nationality, he said.

Thirty police officers are involved in the investigation, 20 of whom are deployed on the streets in and around Northampton.

Yesterday they were stopping and searching cars identified on closed-circuit television using numberplate recognition technology. Specialists from the National Crime and Operations Faculty have also joined the team to assist with forensic work and criminal profiling. Mr Jones said last night that he was very confident of solving the case, even though little useful CCTV footage had been recovered.

“The phone hasn’t stopped ringing with people giving us little nuggets and the odd golden nugget,” he said. “With all the information that we’ve got I’m quite happy to put CCTV on the backburner.”

He said that he was keeping an open mind as to whether the rapists were from Northampton or drove in from elsewhere.

Four of the five victims were initially approached in and around Northampton’s rowdy pub and club quarter. Drunk women can be seen drifting home on their own in the early hours of most mornings, according to Helen Grattan, the manager of The Auctioneer’s pub on Drapery.

“I wouldn’t walk around here on my own at night,” she said. “There’s a lot of dark alleyways that girls could be pulled down and a lot of shady people hanging around on street corners.

“A lot of the women here are really worried now. Last night was dead and it’s normally a really busy one for us.”

Michelle Felton, 27, walked home alone in the early hours the night after the most recent attack. “I went right past where the girl who was clubbed over the head was found but I didn’t know it then. I wouldn’t now — my Mum would kill me.”

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