Police are appealing for information following a series of sexual assaults near a north-west London Tube station.
The assaults took place on three consecutive weekends near Dollis Hill station, Scotland Yard said, and officers are treating the attacks as linked.
A 30-year-old woman was followed by a male at about 11.25pm on August 28 and sexually assaulted in Fleetwood Road, Brent.
Eight days later, on September 5, a 21-year-old woman was sexually assaulted in nearby Ellesmere Road just after 10pm before a member of the public intervened and the suspect ran away.
Then at 10.15pm on September 11 another 21-year-old was sexually assaulted in Ellesmere Road, with the suspect fleeing after a member of the public stepped in.
Each victim described the man as mixed race, slim build, with facial stubble and wearing black clothing.
The officer leading the investigation, Detective Inspector Jonny Newell, noted the attacks took place “on a weekend, at a similar time and in very close proximity to both the Underground and each other”.
“It is clear that the perpetrator is waiting at or near the Tube station with the sole purpose of seeking out women to follow to a secluded area before he carries out his attacks,” Mr Newell said.
“On each occasion the victims have managed to raise the alarm, causing their attacker to flee the scene. We are incredibly grateful to the two members of the public who came to their assistance.
“All of the women have understandably been left shaken and we are doing everything we can to stop this happening again.
“We would urge anyone who lives in the area to think about whether they saw anything suspicious on any of these evenings and to check any CCTV or doorbell footage they may have.
“Sexual assaults of this nature remain very rare but we will of course be carrying out extra patrols in the area over the next few weeks.
“Tackling violence against women and girls is one of the Met’s top priorities and we are determined to stop this man from causing further harm.”
Anyone with information is asked to call 101, giving the reference 8659/11SEP. Information can also be provided anonymously to Crimestoppers by calling 0800 555111.